Research
Workplace Heat and Productivity: The Evidence
Working in the heat is not just uncomfortable: it measurably slows work down. In its 2019 report Working on a Warmer Planet, the International Labour Organization projects that by 2030, heat stress will cost 2.2% of total working hours worldwide, a productivity loss equivalent to 80 million full-time jobs and about US$2.4 trillion a year. This page compiles the verified occupational-heat figures (global, regional, and by sector) alongside how safety agencies define heat that reduces work capacity. Sweating is the body's main cooling response to this heat, which is why heat exposure sits at the center of the story.
By the Sweat Explained Editorial Team · Published 2026-07-13 · Last reviewed 2026-07-13 · Educational information, not medical advice.
Key statistics at a glance
2.2%
of total working hours projected lost worldwide in 2030 because of heat stress
ILO 2019 (assumes 1.5°C rise)
80 million
full-time jobs equivalent to the projected 2030 productivity loss
ILO 2019
US$2.4 trillion
estimated annual global economic loss from heat stress in 2030
ILO 2019
60%
of the projected 2030 working-hour loss falls on agriculture
ILO 2019
~5%
of working hours projected lost in Southern Asia and Western Africa, the hardest-hit regions
ILO 2019
Heat is a measurable drag on work
When the temperature climbs past what the body can comfortably shed, people slow down, take more breaks, and in some jobs stop altogether. The International Labour Organization (ILO) put a number on that lost output. Its 2019 report projects that in 2030, about 2.2% of total working hours worldwide will be lost to heat stress, a productivity shortfall the ILO describes as equivalent to 80 million full-time jobs and roughly US$2.4 trillion in annual economic losses.
That projection rests on a specific assumption: a global mean temperature rise held to 1.5°C above pre-industrial levels by the end of the century. The ILO calls this a conservative estimate, because a larger temperature rise would push the losses higher. The figure is a modeled projection, not an observed count: it estimates what heat exposure is expected to cost, based on climate and labour data.
Which sectors absorb the loss
The burden is not spread evenly across the economy. Outdoor and physically demanding work is hit hardest, because both the exposure and the exertion are higher. Agriculture alone accounts for the majority of the projected loss.
| Group | Value |
|---|---|
| Agriculture | 60% |
| Construction | 19% |
| Other sectors | 21% (manufacturing, services, transport, etc.) |
Source: ILO, Working on a Warmer Planet, 2019. Chart is an original rendering of the cited data.
Where the losses land
Heat stress falls disproportionately on lower-income regions where agriculture employs a large share of the workforce and air conditioning is scarce. Southern Asia and Western Africa are projected to lose about twice the global share of working hours.
| Region | Working hours lost (2030) | Full-time jobs equivalent |
|---|---|---|
| World | 2.2% | 80 million |
| Southern Asia | ~5% | ~43 million |
| Western Africa | ~5% | ~9 million |
Regional shares are roughly double the global figure. Estimates assume a 1.5°C temperature rise and that agricultural and construction work occurs in shade.
How heat actually reduces work capacity
The mechanism is physiological. To keep core temperature near 37°C, the body sheds heat mainly by sweating and by moving blood to the skin. As air temperature and humidity rise, sweat evaporates less efficiently, so a worker must either slow the pace, rest more often, or risk heat-related illness. Lost working hours are the aggregate of all those individual slowdowns and breaks.
Occupational safety agencies quantify the hazard using the Wet Bulb Globe Temperature (WBGT), a heat-stress index that combines temperature, humidity, air movement, and radiant heat. In the United States, the National Institute for Occupational Safety and Health (NIOSH) sets WBGT-based exposure limits: a Recommended Alert Limit for workers who are not yet acclimatized to heat, and a higher Recommended Exposure Limit for those who are. Above these limits, the combined heat load exceeds what most workers can tolerate without health effects, which is why work is expected to slow. Acclimatization (the body adapting over days to weeks) meaningfully raises tolerance, which is one reason the same conditions affect different workforces differently.
How to read these numbers
A few cautions keep the figures honest. First, the ILO totals are projections from a model, not a tally of hours already lost; they combine climate scenarios with labour and productivity data and carry the usual modeling uncertainty. Second, they assume the 1.5°C scenario and that outdoor work happens in shade, so they are best read as a conservative floor, not a ceiling. Third, the sector and regional splits describe where the loss concentrates, not the risk to any individual worker, which depends on the specific job, local climate, hydration, acclimatization, and workplace controls.
The dependable takeaways are directional and well supported: heat stress imposes a large and rising cost on labour; outdoor, physically demanding sectors like agriculture and construction bear most of it; and lower-income tropical regions are hit hardest. None of this is medical advice, and it does not diagnose any individual's heat risk.
What the estimate does and doesn't capture
Understanding the boundaries of the ILO estimate helps avoid over-reading it.
- Included: reduced work capacity across sectors when heat forces a slower pace or more rest, aggregated to national, regional, and global totals.
- Assumed: a global temperature rise limited to 1.5°C, and that agricultural and construction work is performed in shade rather than direct sun.
- Not a personal risk score: the percentages describe economy-wide productivity, not the heat risk faced by any single worker.
- Conservative by design: the ILO notes that higher warming would raise the losses beyond these figures.
Methodology and limitations
Global, sector, and regional figures are taken directly from the International Labour Organization's 2019 report Working on a Warmer Planet: The Impact of Heat Stress on Labour Productivity and Decent Work, cross-checked against the ILO's accompanying news release. The framework for defining heat that reduces work capacity draws on the NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments (DHHS/NIOSH Publication No. 2016-106, February 2016).
Limitations: the ILO numbers are modeled projections for 2030, not observed counts, and they assume a 1.5°C temperature rise with shaded outdoor work; the ILO itself frames them as conservative. Model outputs carry uncertainty and depend on the input scenarios. Regional and sector shares indicate where losses concentrate, not the risk to any individual. This page is general educational data journalism, not medical, legal, or occupational-safety advice; workplaces should follow the guidance of qualified safety professionals.
Frequently asked questions
- How much work will heat stress cost by 2030?
- The ILO projects that 2.2% of total working hours worldwide will be lost to heat stress in 2030, a productivity loss equivalent to 80 million full-time jobs and roughly US$2.4 trillion a year. The estimate assumes global warming is held to 1.5°C.
- Which industries are most affected?
- Outdoor, physically demanding work. The ILO estimates agriculture will absorb about 60% of the projected 2030 working-hour loss and construction about 19%, with the remainder spread across other sectors.
- Which parts of the world are hit hardest?
- Southern Asia and Western Africa, each projected to lose about 5% of working hours in 2030, roughly double the global average. That is equivalent to about 43 million jobs in Southern Asia and about 9 million in Western Africa.
- How do safety agencies measure workplace heat?
- Many use the Wet Bulb Globe Temperature (WBGT), which combines temperature, humidity, air movement, and radiant heat. NIOSH sets WBGT-based limits: a lower alert limit for workers not yet acclimatized to heat and a higher exposure limit for those who are.
- Are these figures certain?
- No. They are modeled projections, not observed counts, and they assume a 1.5°C temperature rise with shaded outdoor work. The ILO describes them as conservative, meaning greater warming would push the losses higher.
- Why does heat slow workers down at all?
- The body keeps its core near 37°C mainly by sweating and shifting blood to the skin. When heat and humidity rise, cooling becomes less efficient, so workers must slow down or rest more to avoid heat illness, and those slowdowns add up to lost hours.
Sources
Primary peer-reviewed studies and official sources first, then reviews and institutional framing (secondary).
- International Labour Organization. Working on a Warmer Planet: The Impact of Heat Stress on Labour Productivity and Decent Work. ILO, Geneva, 2019. Projects 2.2% of global working hours (80 million FTE jobs; US$2,400 billion) lost to heat stress by 2030 under a 1.5°C scenario. ILO report
- International Labour Organization. Increase in heat stress predicted to bring productivity loss equivalent to 80 million jobs. ILO news release, 1 July 2019 (agriculture 60% and construction 19% of the loss; Southern Asia and Western Africa ~5% each). ILO news
- National Institute for Occupational Safety and Health (NIOSH). Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments. DHHS (NIOSH) Publication No. 2016-106, February 2016. Defines WBGT-based Recommended Alert Limits (unacclimatized) and Recommended Exposure Limits (acclimatized). NIOSH
How to cite this page
Sweat Explained. Workplace Heat and Productivity: The Evidence. Published 2026-07-13; last reviewed 2026-07-13. Available at: https://sweatexplained.com/research/workplace-heat-and-productivity-research
Please cite the original studies for the underlying figures. Journalists are welcome to link to this page; the charts are original renderings of the cited data.