The Lost Working Week

Executive summary

Extreme heat is taking working time from the world’s smallest businesses. Lost hours accumulate into lost days, reducing output, interrupting trade, damaging goods, raising costs, and weakening the livelihoods that depend on these enterprises. When heat prevents a proprietor or employee from working, the business may slow down or stop. When customers stay home, goods spoil, or power supplies fail, remaining open may still mean earning less. Addressing extreme heat through small businesses reaches people where they are productive: organizing work, serving customers, managing assets, and generating income. This research brief examines how extreme heat affects that productive activity and what it could take to protect it.

Extreme heat cannot be reduced to a single universal temperature. Its effects depend on humidity, radiant heat, airflow, workload, health, acclimatization, and the ability to reduce exposure. Local expectations also matter because businesses, buildings, and working routines have developed around inherited climate conditions. Yet around the world, across climate zones, climate change is pushing more working time beyond those physiological and practical limits: the share of the global population experiencing at least 90 days of strong heat stress annually rose from 55% in the 1970s to 70% in 2015–2024 1 ; by 2050 many tropical and subtropical regions could experience dangerous Heat Index conditions on one-quarter to one-half of all days. 2

This brief focuses on owner-operated, non-agricultural businesses containing one to nine workers, whether formal or informal. These businesses account for nearly half (46.8%) of non-agricultural employment across a 99-country sample. 3 Evidence from several settings suggests that the smallest businesses are especially vulnerable to rising temperatures. They often have limited financial reserves, little redundancy among workers, and restricted control over their premises, hours, power supply, or surrounding infrastructure. Caribou’s rapid survey of 903 small businesses across seven countries provides a direct business-level view of these pressures. Of participating businesses, 53% reported losing trading time to heat during the previous year, and more than one in five of those asked to count cumulative days closed had lost the equivalent of at least a working week.

These findings show why lost working time deserves greater attention from the climate response. Businesses are already adapting by changing hours, moving work, buying fans or cooling equipment, improving ventilation, protecting stock, and absorbing higher electricity and operating costs. Much of this response is financed from cash flow, household savings, or informal borrowing, and continued spending does not necessarily provide adequate protection. Existing climate and cooling initiatives offer relevant technologies, delivery experience, and financing approaches, but activity remains fragmented. Small businesses have yet to become a consistently recognized unit through which funders, providers, and public institutions organize and evaluate heat adaptation.

Two different businesses, same heat

Extreme heat is taking vital working time from small businesses—the enterprises that underpin economies and support millions of livelihoods around the world. From Lagos to New York, from Ahmedabad to London, people like Kavita and Abeer are trying to keep their doors open but finish each hot day further behind.

Kavita | Ahmedabad, India

Kavita runs a pooja-supplies stall near the Kalupur Swaminarayan temple in Ahmedabad, selling items for Krishna idol worship (clothes, decorations, and related goods). She has been in business there for 10 years out of a makeshift stall built with a tarpaulin/tent-cloth roof rather than a permanent structure.

Ahmedabad’s heat has intensified over the last five years, with temperatures hitting 45–47°C (113–116.6°F) and barely cooling even by midnight. The heat is made worse by humidity after rain. Kavita’s stall has no fan or cooling system, and she suffers real health effects; low stamina, dizziness, fever, vomiting, diarrhea, and headaches that sometimes force her to close and just lie down. The heat also hits her financially: customers avoid stopping at an unshaded stall in peak heat, cutting her customer base by 50% or more and costing her four to five hours of lost business each afternoon.

“After twelve or one o’clock, it goes over 45 [°C]. Then you think: do we stay or not? Because of the heat we lose four or five hours. That’s a big loss for us.”

Abeer | London, UK

Abeer runs Ola–Pinch of Yemen, a street food truck that’s only 2.5 years old and cooks everything fresh to order. The truck includes a grill, cooker, and other appliances, making the business vulnerable to summer heat.

Extreme heat makes the trailer nearly unbearable to work in. Abeer has had to close for a full week (losing that income entirely), suffers headaches and near-fainting, and now manages by taking frequent breaks and drinking water—all while sales drop because fewer customers want to eat out on very hot days. The council doesn’t allow high electrical usage, so Abeer cannot install fans or air conditioners from power outlets. What would help her and other street-food traders most is stronger electricity access to power fans, ventilation, or insulation to make the heat manageable.

“Because of the heat, I had to close for one week, because work was impossible… That week I closed was lost. That’s it. I had to. […] You have to keep going. You can’t stop, you know? I have to pay rent.”

Beyond these individual stories, the sheer scale of the crisis is staggering: during extreme heatwaves, the net earnings of some of the world’s smallest businesses can plunge by an immediate 40%. 4 Extreme heat goes beyond a simple loss of comfort. Rising temperatures impose more frequent physical bottlenecks on operations. Empirical evidence shows that in climate-exposed sectors, businesses can lose up to an hour per worker, per day, once temperatures cross 29.4°C (85°F). 5 Lost hours compound to lost days, and lost days to lost weeks—a severe, involuntary contraction of a small business’s primary productive asset.

This is the moment to identify, finance, and scale practical ways of protecting the working time and livelihoods of small businesses.

Defining extreme heat

Extreme heat and the human body

One way to define extreme heat is to identify conditions above which there is stress or harm to the human body, which works to maintain its core temperature within a relatively narrow range. Above a certain thermal load, people struggle to move, to think, and to work. At higher levels, heat can become fatal.

There is more than one way to measure, compare, and warn people about these thermal loads.

• One approach comes from occupational safety. An individual’s experience of heat depends on the conditions at that moment, including humidity, radiant heat, airflow, workload, hydration, and rest, as well as on their own physiology. These ambient variables are unified under the Wet Bulb Globe Temperature (WBGT), an empirical index specifically designed for work-activity assessments that integrates air temperature, relative humidity, wind speed (air movement), and radiant heat (such as solar exposure). 6 Because WBGT correlates environmental heat directly with a person’s metabolic physical effort across different occupational intensities, 7 it provides a highly accurate measure of physical work capacity loss. Readings above 28°C (82.4°F) WBGT are widely considered dangerous. 8 Surpassing this threshold impairs internal thermal regulation and triggers a transition from mild behavioral discomfort to severe physiological strain, including heat exhaustion and heat stroke. 9
• A distinct yet complementary approach comes from climate science. Climatologists and mapping agencies like Europe’s Copernicus rely on the Universal Thermal Climate Index (UTCI) to assess broad geographical population exposure over time. 10 UTCI does not establish rigid industrial safety limits; rather, it is a “feels-like” bio-meteorological model that simulates how a human body dynamically adapts its thermal balance in an open environment. Copernicus designates 32°C (89.6°F) UTCI as the active threshold for “strong heat stress.” UTCI is useful for comparing population-level heat exposure across places and over time, and for identifying where heat-adaptation and public-health resources may be needed. In Pakistan, an initiative supported by the European Space Agency combines daily UTCI data with high-resolution population data to map heat risk nationwide and feed an Asian Development Bank decision-support platform, illustrating how thermal-stress measurement can inform urban adaptation and public-health investment. 11
• A third approach is perhaps the most straightforward: pick a number. HERA uses a flat 35°C (95°F) absolute air-temperature threshold to communicate immediate urban risks on the ground. 12

These approaches are different. WBGT and UTCI were developed for different purposes and use different scales, while HERA’s 35°C (95°F) measure centers on air temperature. These thresholds should therefore not be compared as if they represented equivalent levels of physiological stress.

Heat vulnerability varies with age, health, acclimatization, workload, fitness, body size, and a person’s ability to reduce their exposure. Evidence on heat and biological sex outside pregnancy is mixed and incomplete. Controlled studies do not consistently show that healthy girls or younger women are inherently less able than comparable boys or men to regulate heat. 13 Newer research, however, suggests that women may reach unsafe physiological limits sooner in middle and older age. 14 Pregnancy is a distinct and well-established period of vulnerability, with heat exposure associated with adverse maternal, fetal, and neonatal outcomes. 15 The wider relationship between sex and heat vulnerability remains unsettled, not least because women are underrepresented in heat-stress research 16 —a gap that should be rectified. As discussed later, gendered patterns of work may also concentrate women in livelihood roles that expose them to greater heat risk and leave them with fewer options for reducing that exposure.

Extreme heat and location

Location matters because a fixed physiological threshold and a locally defined “heatwave” address different experiences. On the Universal Thermal Climate Index, a value of 32°C (89.6°F) or above indicates strong heat stress wherever it occurs. 17 In the 2010s, Ahmedabad experienced these conditions on an average of 316 days a year, nearly seven times New York City’s 46 days. 18 Conditions that are episodic in New York City are therefore routine across much of the year in Ahmedabad. But routine does not mean safe: the same thermal load can strain the human body in either city. Nor does this comparison mean that every strong-heat-stress day in New York City constitutes a heatwave, or that Ahmedabad must cross into a higher UTCI category before experiencing one.

Lagos illustrates the other edge of this changing boundary. Caribou’s analysis indicates that the city experienced an average of 336 strong-heat-stress days a year from 2010 to 2020—more even than Ahmedabad—leaving little room to move work into a cooler season and, on the hottest days, few cooler hours into which it can move. 19 In Lagos State, where 76.3% of employment was informal in 2023, that constraint falls directly on livelihoods and small businesses operating with limited protection or capacity to absorb lost working time. 20

Thus, heatwaves (a different way of describing extremes) are generally defined using locally specific thresholds, reflecting both departure from the climate normally experienced in that place and the persistence of unusually hot conditions across successive days and nights. 21 Historical climates have shaped each city’s infrastructure, working hours, cooling practices, expectations, and understanding of what constitutes “extreme” heat. Put bluntly, conditions that can prompt emergency warnings and front-page headlines in New York City may be an ordinary Tuesday in Ahmedabad or Lagos. However, this does not mean the conditions are benign. Climate change is now pushing beyond the norms inherited in both places—making unusual heat more frequent in some and leaving fewer safe hours for work and recovery where severe heat is already commonplace.

But climate change is undermining these routines, including the rhythm of the working day. 22 Warming is increasing the intensity, reach, and duration of heat stress. More days are crossing dangerous thresholds, and warmer mornings and nights reduce the cooler intervals available for work and recovery. Three signals illustrate the direction and scale of the change:

• The hottest conditions are getting hotter. A 2026 global UTCI analysis finds that the hottest daytime and night-time “feels-like” conditions have warmed by approximately 0.3°C (32.54°F) per decade since the 1970s. 23
• More people face both sustained and extreme heat stress. The share of the global population experiencing at least 90 days of strong heat stress annually—UTCI at or above 32°C (89.6°F)—rose from 55% in the 1970s to 70% in 2015–2024. Separately, the share experiencing at least one day of extreme heat stress—UTCI at or above 46°C (114.8°F)—rose from 16% to 22%, representing approximately one billion additional people. 24
• The number of dangerous days is projected to increase sharply. By 2050, many tropical and subtropical regions could experience dangerous Heat Index conditions on one-quarter to one-half of all days. 25

In this brief, “extreme heat” does not refer to a single universal temperature. It refers to conditions that push beyond the physiological and practical limits within which people and small businesses can work safely and effectively. That boundary moves: it depends on the person, the intensity of the work, humidity, radiant heat, airflow, acclimatization, and the infrastructure and routines that have developed around a place’s historical climate. A temperature can therefore be dangerous without being locally unusual, or locally extreme before it crosses a universal physiological threshold. No one number fully expresses extreme heat. Hot places start with greater absolute exposure; historically cooler places often start with less heat-ready infrastructure. Climate change is pressing on both vulnerabilities. Across the measures and cities examined here—from New York and London to Ahmedabad and Lagos—the direction of travel is unmistakable: the number of hours, days, and weeks that become too hot for business as usual is increasing.

The heat threshold differs among people, activities, and places, but the pattern is shared: as conditions warm, more working time is pushed beyond the range around which businesses, buildings, and daily routines were formed.

In sum, while both precise definitions and personal experiences of heat may vary, the direction of travel is clear and concerning. People, households, and businesses will spend more days each year under conditions experienced as extreme heat. Hot places start with greater absolute exposure; historically cooler places often start with less heat-ready infrastructure. Yet both are being pushed away from the conditions around which they formed.

Defining micro and small enterprises

Heat impacts almost every element of human society. This brief focuses on small businesses, because a large share of the world earns a living through self-employment and small enterprises.

“Micro and small enterprises” (MSEs) is the formal term for this target population, and “small businesses” is its plain-language equivalent. Both terms refer to owner-operated, non-agricultural enterprises containing one to nine workers, formal or informal. The categories “small and medium-sized enterprises” (SMEs) and “micro, small, and medium-sized enterprises” (MSMEs) include larger enterprises of up to 300 employees, and so are not used in this research. Additionally, “micro-enterprise” on its own can imply only the smallest, self-employed end of a population that also includes businesses supporting employees; thus, the combined term MSEs is used. Building on ILO data, Caribou estimates that MSEs of this size account for nearly half (46.8%) of non-agricultural employment across the ILO’s 99-country sample. 26

These definitions come with two important caveats:

1. Primary agricultural production—including crop farming, livestock, forestry, fishing, and smallholder farms—is outside the target population. Agricultural evidence may still be used where it illuminates shared exposure or response mechanisms, but it should be identified as adjacent rather than treated as evidence about the target itself. Non-agricultural agrifood businesses—including processing, storage, transport, repair, food service, trade, and retail—remain in scope.
2. The distinction between a formal, registered enterprise and an informal self-employed person can be blurry. At one end is someone earning income independently, with little distinction between household and business finances. At the other is a registered enterprise with separate books and, perhaps, several employees. Both ways of earning a living matter in the overall tapestry of the economy, and both remain in scope. The center of analytical focus, however, is the more distinct enterprises, particularly those that support employees.

The world of small business is large and diverse, encompassing retail shops, traders, wholesalers, transport providers, small-scale manufacturers, service businesses, and hundreds of other vocations. The resilience of these businesses is therefore important to livelihoods and to the wider functioning of the economies in which they operate.

Many small businesses face recurring constraints: limited access to finance 27 ; low productivity, partly due to limited management capabilities and business practices 28 ; and difficulty acquiring skills or recruiting suitable employees. 29 These constraints vary by country, sector, and enabling environment, but together they can leave MSEs with limited financial and operational buffers.

How small businesses experience heat

Extreme heat reaches small businesses through several pathways. It acts on the people who run and staff them, the customers who sustain them, the goods they sell, and the power and cash they depend on. This section sets out existing research about each of those pathways, then turns to what small businesses themselves reported. Before examining those pathways, it is important to establish why the resulting disruption is likely to fall hardest on the smallest businesses.

Heat hits smaller businesses harder

Evidence suggests that smaller businesses are more vulnerable to losses in productivity and revenue as temperatures rise.

• In Indonesia, a 1°C (33.8°F) increase in average temperature was associated with a fall of up to 22% in revenue per worker among household micro-enterprises, while firms with ten or more workers experienced no statistically significant loss. 30
• An analysis of more than 2.7 million firms across 23 advanced economies found that high temperature days and heatwaves reduce labor productivity more severely among the smallest firms. Ten additional days above 35°C (95°F) were associated with a 0.3% reduction in annual labor productivity. An extra heatwave lasting at least five days was associated with a 0.2% reduction. 31
• Globally, the ILO estimates that heat stress could reduce total working hours by 2.2% by 2030, equivalent to 80 million full-time jobs. With agriculture accounting for about 60% of the projected loss, these totals provide context rather than estimates for the non-agricultural businesses examined here. 32

Together, this evidence points to a double disadvantage for MSEs: they appear to lose more when temperatures rise, and they often have less room to absorb the disruption. 33 Where a proprietor or small group of employees covers several business functions, lost working time can affect the whole operation. Heat does not create all the underlying financial and operational constraints small businesses face, but it can make them harder to manage.

How heat exposure leads to business losses

Small businesses experience heat in several modes, distinguished by enclosure and access to air conditioning. These are neither fixed market categories nor stages, but rather, fluid context-based segments. An enclosed business without air conditioning may be kept cooler through passive design, ventilation, fans, or other low-energy measures, while an air-conditioned business may become dangerously hot during a power cut. Nonetheless, these segments distinguish different patterns of exposure and different options for responding.

• Outdoor businesses: Most earning activity takes place outdoors or in open structures, as with roaming traders, motorcycle transport providers, roadside vendors, and market traders. These businesses have little control over ambient and radiant heat, especially when work takes place in direct sunlight. Protection therefore tends to be portable, shared, or place-based, including shade, canopies, airflow, hydration, rest, and changes to working hours. 34 Heat can therefore reduce the usable earning hours in the day. 35
• Enclosed businesses without air conditioning: Most activity takes place within a bounded space without air conditioning, such as market stalls, kiosks, workshops, offices, and storefronts. Enclosure may provide shelter from direct sun while trapping heat and limiting airflow. But these businesses need not remain uncooled. Their roofs, walls, openings, equipment, and energy supply create opportunities for external shade, cool roofs, better ventilation, efficient fans, evaporative cooling where appropriate, and selective cooling. This is a particularly important opportunity to protect working capacity without making conventional air conditioning the default response.
• Businesses with air conditioning: Air conditioning can protect working capacity, health, and temperature-sensitive goods, although heat exposure outside the workplace can still contribute to absent employees and missing customers. 36 Protection depends on affordable equipment, reliable electricity, maintenance, and efficient technology. A power cut, equipment failure, or unaffordable electricity bill can return a business abruptly to the heat. The challenge is to make air conditioning efficient, reliable, affordable, and increasingly powered by lower-carbon electricity where it is needed.

Cooling solutions across all three environments are easier to deploy where businesses have reliable grid electricity, but this cannot be assumed. If the current pace of electrification continues, 660 million people, most of them in Africa, will remain without electricity in 2030. Where cooling requires power, businesses may instead depend on solar home systems, mini-grids, or generators. In these settings, the power supply shapes which forms of protection are within reach, while appliance efficiency determines whether equipment such as a fan or refrigerator can run on the power available. 37

These segments describe where and under what conditions businesses operate. Across all three, heat becomes business loss through four overlapping pathways: the people who keep a business operating, the customers who sustain it, the goods it sells, and the power it relies on and costs it must absorb.

Workers

Heat reduces the hours available for physical work. In a solo enterprise, every hour in which the proprietor cannot work may also be an hour in which the business cannot trade. In an enterprise with several employees, lost working time may mean slower output, reduced service, shorter opening hours, or closure.

• Daily surveys of nearly 400 informal workers in Delhi found net earnings are roughly 40% lower on heatwave days. The same research estimates that, over a year, outdoor informal workers in urban India lose approximately 24 workdays due to heat-related illness, reduced productivity, and workplace closure, while workers in poorly ventilated indoor workplaces lose nearly 15. These are estimates of worker-days rather than business operating days, but they show how heat can reduce the labor available to the smallest enterprises. 38
• In Indian manufacturing, climate control on the factory floor protected output per worker but did not eliminate absenteeism, because workers remained exposed at home and outside the workplace. 39
• Time-use evidence from the United States shows workers reallocate time away from exposed labor on hot days. 40

Customers

Heat also changes who shops, when they shop, and where they shop.

• Research on transactions from Seoul finds that heatwaves shift consumption between online and offline channels rather than uniformly reducing it. 41
• During the June and July 2026 UK heatwaves, high-street footfall fell by 6.2% and 3.8% year on year, while air-conditioned shopping centres and retail parks declined far less or held steady. Online sales reached their highest share of the year. 42

Goods

For businesses that handle perishable goods, heat directly threatens stock and increases the importance of refrigeration and cold storage.

• For indigenous-crop vendors in Durban, South Africa, crop perishability was a statistically significant predictor of income loss, while limited storage access was associated with substantial but only marginally significant additional losses. The study examined several compound shocks rather than isolating the effects of heat, so it supports the perishability and storage mechanism rather than providing direct evidence of a heat effect. 43
• Fewer than 10% of perishable foods worldwide have access to a cold chain, the temperature-controlled storage and transport system that keeps goods fresh, and at least a quarter of food produced in developing countries is lost for want of one. 44

Power and costs

Cooling is itself an operating cost, one that rises when temperatures and cooling needs are greatest. Growing demand for mechanical cooling can strain electricity grids during peak periods, leaving businesses that depend on refrigeration or air conditioning exposed to both higher costs and interruption risk. 45 Where the grid is absent or unreliable, efficiency matters twice. An efficient appliance costs less to run, and it needs a smaller solar system or less generator fuel to run at all. 46

Small businesses describe the impact of extreme heat

To examine how these pathways appear in practice, in August and September 2026 Caribou partnered with two longstanding research collaborators, Aareton Blue Africa and Yazi, to survey 903 small businesses. The combined sample covers seven countries: country samples in Kenya, Malawi, Nigeria, South Africa, and Uganda, and metropolitan samples in New York City, London and South East England, Gauteng, and Lagos. The partners used complementary, convenience-based recruitment approaches to reach a varied set of enterprises, including outdoor and mobile traders as well as businesses operating primarily from fixed premises.

As a rapid first inquiry, the research provides a direct business-level view of how extreme heat is affecting operating time, working capacity, customers, goods, costs, and responses. Further research should use harmonized instruments and representative sampling to more consistently measure lost working time and capture power reliability, workplace conditions, cooling and appliance use, and the costs of adaptation. This approach would help distinguish recurring experiences within these samples from wider patterns and support the design of interventions around how small businesses actually operate. 47