The Growing Need to Protect Workers from Extreme Heat

In June, the heatwave that swept across Europe claimed an estimated 2,300 lives in 12 major cities. According to a rapid analysis by the World Weather Attribution group, two-thirds of those deaths — about 1,500 — were directly linked to climate breakdown, which pushed temperatures up to 4°C higher than they would have been without human-driven global heating [1]. The fact of the matter is that extreme heat is now a pervasive global issue, and one that must be factored into employers’ considerations regarding employee safety. Even in generally temperate countries like the UK and Ireland, the figures are striking, with temperatures above 40°C recorded in the UK in 2022 and above 33°C in Ireland in the same year. As the climate around us shifts out of recognisability, a fundamental rethink of workplace safety, infrastructure, and policy is vital.

The Threat

Across both the UK and Ireland, policy has been slow to adapt. Unlike cold weather, where a minimum workplace temperature of 16°C is mandated by the Health and Safety Executive, no upper threshold currently exists for when it is too hot to work safely indoors [2]. This is increasingly untenable. Heat stress doesn’t just pose a medical risk to vulnerable workers. It impairs judgment, drains productivity, and raises the likelihood of fatal errors, all while pushing infrastructure, supply chains, and employer liability to their limits.

According to the World Health Organization, extreme heat could cost the global economy over $4 trillion in lost productivity every year by 2030, with two per cent of all working hours projected to vanish due to heat stress alone [3]. In the US, a recent report estimated that heat events already account for 235,000 emergency department visits and more than 56,000 hospital admissions each summer, tacking on an extra $1 billion in healthcare costs annually [4].

As Dr Talia Varley, physician lead for Global Corporate Advisory at the Cleveland Clinic, puts it, “Extreme heat events may be the new norm. And companies have more than one reason to be worried” [5].

The Effects

The physiological dangers of extreme heat are well-documented. At a basic level, the human body relies on evaporative cooling — sweating — and increased blood flow to the skin to manage rising internal temperature. When this natural thermoregulation fails, heat stress sets in. This can manifest in various ways: heat rash, cramping, dehydration, disorientation, heat exhaustion, and in the worst cases, heat stroke, which can lead to brain dysfunction or death [6].

But the threat is not merely biological. In high-heat conditions, workers become more irritable, less focused, and more prone to errors. Fine motor skills — the kind required to type, weld, or operate machinery — degrade. Cognitive performance drops. Studies from Harvard University and the Institution of Mechanical Engineers have found that indoor air quality and ambient temperature are critical factors in focus, reaction speed, and decision-making [7]. At temperatures above 25°C, attention, task accuracy, and risk assessment begin to decline. At 30°C and above, the risk of workplace accidents increases significantly [8].

This means the health and safety implications of rising temperatures are just one side of the ledger. There are business continuity, economic performance, and human resource retention issues too.

So how can employers begin to meet this challenge?

The Role of Employers

The first step is to acknowledge that temperature thresholds alone don’t tell the full story. Heat stress results from a combination of environmental, occupational, and personal factors. It’s not just how hot it is outside, but how humid it is, whether there’s airflow, how physically demanding the job is, and whether the worker is elderly, pregnant, taking medications, or managing chronic conditions like diabetes or hypertension. Even clothing plays a role. Those wearing personal protective equipment (PPE), for instance, experience significantly higher internal temperatures [9].

The most accurate tool to assess risk is a wet bulb globe temperature (WBGT) meter, which takes into account not just air temperature, but humidity, radiant heat, and wind speed. Yet very few workplaces in the UK or Ireland currently employ such measures [10].

What’s needed, says Varley, is a systemic approach. “Employers should incorporate heat-related illness prevention into broader health and safety programmes. That means developing a long-term heat-health action plan, tracking temperatures, adapting work schedules, and designing infrastructure for thermal comfort — not just cost efficiency” [11].

This isn’t just a concern for outdoor workers. Office spaces are not immune. Thermal discomfort can have cascading effects on mood, concentration, and morale. Many buildings lack adequate HVAC systems to stay within the temperature range recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) [12]. Moreover, the current standards are typically based on male metabolic rates, which neglect the different thermal preferences and vulnerabilities of women. Women, particularly post-menopause, are more susceptible to sudden temperature changes due to reduced oestrogen production [13].

What’s more, as Arjun Gupta, creator of the indoor air quality device Vyana, notes: “Research shows worker performance declines above 25°C, and high CO2 levels can halve cognitive function. Investing in air filtration, monitoring, and HVAC upgrades isn’t just about comfort. It’s about operational effectiveness” [14].

What’s Being Done?

In the US, some states are taking heat safety seriously. Minnesota, Oregon, and California have implemented laws requiring temperature-specific protections for indoor and outdoor workers, such as mandatory rest breaks, hydration schedules, and shaded recovery zones [15]. Federal rules proposed by OSHA would require employers to provide shaded or air-conditioned breaks once temperatures hit 27°C, with more frequent breaks and monitoring above 32°C [16]. Yet in the UK, practically nothing has changed since the Climate Change Committee reported in March 2023 that the country had made “little progress” on adapting buildings for a warmer climate [17].

It’s not just regulation that’s lagging. According to Brian Castrucci, CEO of the de Beaumont Foundation and a member of the US National Commission on Climate and Workforce Health, only 17% of CEOs surveyed by PwC have implemented strategies to protect their employees from heat-related risk despite more than 65 million American workers already exposed to it [18]. “Extreme heat has come to Main Street, and it’s impacting Wall Street,” Castrucci says. “The question is not whether CEOs are going to feel the heat, but when” [19].

For businesses in the UK and Ireland, this should be a wake-up call. As Jamie Hailstone writes in Forbes, “Companies urgently need to develop strategies to protect workers from excessive heat as average global temperatures continue to rise” [20]. The risks are stark. In October 2024, eleven factory employees were swept away in flooding caused by Hurricane Helene in the US, a tragic reminder that extreme weather is no longer confined to seasonal or outdoor labour [21]. This point is only being further hammered home by the current tragedy unfurling in Texas in the wake of extreme flooding.

As climate hazards intensify, businesses must adopt climate resilience as part of core strategy, not as an ESG side project. That includes upgrading ventilation systems, implementing remote working protocols during red weather alerts, offering heat-related sick leave, and supporting mental health during climate-related disasters. “Effective leadership demands empathy and proactive support,” says Dalya Perez, former senior programme manager at Microsoft. “Publicly acknowledging the challenges faced by impacted employees — for instance, through company-wide messages of support — is a powerful gesture. It lets the team know it’s okay to be human” [22].

The mental health dimension of heat cannot be ignored. According to the American Psychological Association, high temperatures increase irritability and aggression, exacerbate depression, and can trigger psychotic episodes in vulnerable populations [23]. That psychological stress, layered onto physical discomfort, compounds the risk of burnout, mistakes, and absenteeism.

Planning ahead is crucial. Hansi Singh, CEO of Planette.ai, a climate forecasting startup, argues that “the perception of limited warning often stems from a lack of attention to forecasts. With better planning and integration, much of the human toll from extreme weather could be avoided” [24]. Singh is already working with insurers to develop parametric insurance products for workers whose livelihoods are disrupted by extreme weather. She predicts such schemes will become mainstream across the Global North in the coming decade [25].

Action Points

So what can businesses do now? Start by assessing the specific risks to their sector, workforce, and geography. Engage in training programmes that educate both workers and managers on the signs of heat illness, acclimatisation protocols, and emergency response. Invest in building adaptations and real-time monitoring tools. Establish internal communication strategies for red alerts. And design climate contingency policies — including remote work, staggered hours, or even temporary closures — that prioritise health over output.

It’s tempting to think of extreme heat as someone else’s problem, a challenge for vineyards in Spain or solar farms in Arizona. But the climate is shifting everywhere. In the immediate moment, it’s tempting to celebrate the uncharacteristically warmer temperatures that make for a nicer summer. But this is just the tipping point. As the world continues to warm, soon there will be far grander issues facing even countries with traditionally moderate climates. Workers will need to be protected.

As Dr Tim Fox, lead author of the Institution of Mechanical Engineers report on heat stress, warned: “Adapting industries to, and preparing them for, a warmer world will be essential for the future successful functioning of societies of all nations” [26]. In the coming years, success won’t just be measured in profits and productivity, but in how well we protected the people doing the work.

Protecting Workers from Extreme Heat

As temperatures continue to rise and the frequency of extreme heat events escalates, the case for immediate and sustained employer action is overwhelming. Protecting workers from heat stress is no longer a seasonal concern but a year-round responsibility, requiring investment, foresight, and a shift in how we define workplace safety. The economic, ethical, and human costs of inaction are simply too high. Those businesses that lead with empathy, science, and resilience will not only safeguard their workforce but also secure long-term operational stability. The climate has changed. Now, the workplace must too.