Extreme weather and temperatures at work

Extreme weather events

Employers in the UK have a legal and moral responsibility to manage risks associated with extreme weather events under the Health and Safety at Work Act 1974, which requires them to take reasonable steps to protect employees from harm. 

This includes conducting thorough risk assessments that consider hazards such as icy surfaces, flooding, heatwaves, and high winds, and implementing measures to mitigate these risks, especially for vulnerable workers.

Employers should not encourage staff to travel for work when it is unsafe to do so and official warnings advise against it. Under the Employment Rights Act 1996, employees are protected from detriment if they refuse to attend work due to a reasonable belief of serious and imminent danger. It is important to engage with your UNISON Health and Safety representatives and regional staff when making decisions on these protections.

Clear communication is essential, ensuring staff understand emergency procedures, safety protocols, and reporting processes. Good employers will have developed a policy on extreme weather events. The policy should outline risk assessments, emergency procedures, remote working options, pay and leave rules, and communication strategies. Ultimately, managing extreme weather is about balancing safety, flexibility, and clear guidance, ensuring that employees are not exposed to unnecessary risks.

The International Labour Organization’s (ILO’s) Ensuring Safety and Health at Work in a Changing Climate: A Global Report found that global occupational safety and health (OSH) protections have struggled to keep up with the evolving risks from climate change, resulting in worker mortality and morbidity. These risks include excessive heat, UV radiation, extreme weather events, workplace air pollution, vector-borne diseases, and agrochemicals.

Your employer should monitor the Heat-Health Alert (HHA) colour warning system and discuss potential health and safety impacts with health and safety representatives. As UNISON members deliver public services across the UK, some areas may have different levels of weather warnings in place. Therefore, local authorities may issue guidance relating to their local circumstances and demands on local health services. Health and Safety law requires employers to ensure that, so far as reasonably practicable, they do all they can to protect the health, safety, and welfare of their staff. This includes protecting them from the risks of excessive heat and cold. Employers need to take all reasonable steps to achieve a temperature that is as close as possible to comfortableTemperatures at Work

What is meant by 'thermal comfort'?

The human body normally tries to maintain a core temperature of around 37°C to 37.5°C. This means that the environment around us can have varying effects on our body’s ability to maintain (regulate) a state that does not cause us to become aware or concerned about feeling too hot or cold, referred to as a state of thermal comfort.

The Health and Safety Executive (HSE) states:

“Thermal comfort is not measured by room temperature, but by the number of employees complaining of thermal discomfort.”

So, it is important to remember that room temperature alone is not an indicator of thermal comfort, as we are all individuals; therefore, one size (or temperature) does not fit all.

Cold exposure risks

Prolonged cold can reduce blood flow to extremities, causing chilblains, Raynaud’s disease, and white finger. Severe cases may lead to frostbite, permanent tissue damage, and fatigue as the body expends energy to stay warm. Numb fingers, bulky clothing, and icy surfaces increase accident risk. Extreme cold can cause hypothermia, unconsciousness, coma, and cardiac arrest.

Heat exposure risks

Excessive heat can cause tiredness, muscle cramps, and strain on the heart and lungs, increasing accident risk. Prolonged exposure may lead to flushed skin, heavy sweating, dizziness, nausea, vomiting, rapid heartbeat, confusion, and reduced urine output. Without cooling and hydration, this can progress to heatstroke a life-threatening condition where body temperature exceeds 40°C. Heatstroke can cause organ damage or death and requires immediate emergency care. Outdoor workers also risk sunburn, premature ageing, and skin cancer.

Other factors

Uncomfortable temperatures can cause irritability, fatigue, and reduced concentration. People with certain conditions (heart/kidney disease, diabetes, asthma), those who are young, older, pregnant, on medication, or experiencing menopausal hot flushes may be more vulnerable.

Indoor temperature

Generally, the acceptable comfort range for most types of work is between 16°C and 24°C. The Chartered Institute of Building Services Engineers recommends 16°C for factories, 18°C for hospitals, and 20°C for offices. Heavy work in factories may make 13°C comfortable, whereas very sedentary work may still be performed with reasonable comfort around 24°C.

However, there are many factors that affect our sense of whether we feel too hot or cold. This is called our ‘thermal comfort’. In addition to air temperature, these include heat radiated from hot objects (eg, pipes or machinery), air movement, humidity, clothing, and the rate of work or physical exertion required.

With no specific legal maximum, employers must, under the law, provide a working environment that is, so far as reasonably practicable, safe, without risks to health, and which has adequate welfare facilities. Approved Codes of Practice (ACoPs) provide practical examples of compliance and explain what is “reasonably practicable” or “suitable and sufficient”.

Employers have a duty to assess risks from extreme temperatures, ventilation, and sun exposure in the same way as any other workplace hazard. For more details, see UNISON’s guidance on risk assessments.

Normally, the temperature should be at least 16°C, unless the work involves rigorous physical effort, when the minimum is 13°C. However, other factors (heat radiated from hot objects, air movement, humidity, clothing, and physical exertion) mean these temperatures may not be comfortable. If a reasonable temperature cannot be achieved, local heating or cooling should be provided.

Regulation 6 of the Workplace (Health, Safety, and Welfare) Regulations (WHSWR) requires effective and suitable ventilation of enclosed workplaces with sufficient quantities of fresh or purified air. The Approved Code of Practice (ACoP) states that ventilation should replace stale, hot, or humid air at a reasonable rate.

Regulation 7 of WHSWR requires the temperature of workplaces inside buildings to be reasonable. They should also be adequately insulated where necessary, taking into account the type of work, and to avoid excessive effects on temperature from sunlight. Methods of heating or cooling must not allow fumes, gas, or vapour into the workplace if likely to cause injury or harm. Sufficient thermometers should be provided to allow employees to check the temperature in any indoor workplace.

The temperature in toilets and rest areas should be reasonable. Changing rooms and shower rooms should not be cold. Temporary heating and cooling should be provided in normally unoccupied rooms such as storerooms, if other than for short periods.

Inside, when it is too hot, ventilation can be improved by providing fans (note that they are ineffective at cooling air when it is above 27°C) or portable air cooling cabinets, and by opening and shading windows. Job rotation, frequent rest breaks in a cool place, and cool clean water may also be appropriate; as may taking the hottest rooms out of use during extreme periods of temperature.

Where it is too cold inside, the employer must meet at least the legal minimum unless impractical because of food, other cold processes or products, or the need for being open to the outside.

Working outdoors

The WHSWR do not apply to outdoor workplaces or working outdoors, but employers still have general duties to ensure health and safety under the HSWA 1974, and duties to assess and control risks from work under the MHSWR. These legal requirements cover both working outside in the cold and in the sun and/or heat (see UNISON’s separate guidance on risk assessments – see access below).

If the work is outside during hot and/or sunny weather, working hours should be adapted or the work altered to minimise exposure to the sun or heat; possibly avoiding or shortening work outside during the hottest part of the day or providing shade for this work. Sun protection creams, long sleeves, clothes with close weaves, and wide-brimmed hats may also help, as may job rotation, where workers take turns to do a particular job.

Key health and safety points

Employers must conduct risk assessments and prevent, so far as reasonably practicable, or otherwise control the risks to workers’ health and safety, including exposure to excessive heat, cold, or the sun. There are a number of steps which can be taken; some temporary to deal with unusual weather, others more permanent for recurring situations.

Employers must take into account individuals who may be more vulnerable to harm. This consideration might apply to the extent of exposure allowed and also to giving some workers more frequent rest breaks or allowing them to leave work early. Reasonable adjustments must be made for disabled and pregnant workers and all people covered by the Equality Act.

It is crucially important that risk assessments and emergency procedures are reviewed regularly across public services, especially in safety-critical environments.

Regardless of thermometer readings, if people are complaining of the heat or cold indoors, then common sense says that it is too hot or cold and something should be done.

Personal protective equipment (PPE), which should be the last resort, where used to protect from the cold, should not just be the cheapest available. Several layers and adaptable clothing (unzippable vents, breathable materials, etc.) will allow workers to lose body heat as they get warmer with vigorous work.

It might be necessary to get a competent heating and ventilation engineer to do a full survey of workplace temperatures, humidity, air movement, and current heating and ventilation systems—so that a permanent solution can then be recommended.

Jobs or work areas can be redesigned to remove staff from the source of heat as much as possible, for example: reducing heat gain via windows by reflective film or blinds, insulating hot pipes and equipment, possibly reducing window area, and if necessary moving desks and workstations away from windows.

Staff who may still be at risk from exposure to excessive heat, cold, or sun should be trained and/or given information on what to look out for (both exposure risks and symptoms) and what steps to take to avoid these or if they occur.

PPE must be provided by law free of charge to employees they cannot be charged for its supply for use at work or be asked for a deposit. Suitable protective clothing and rest facilities should be provided where local heating or cooling does not give reasonable comfort. Where practical, systems of work such as task rotation should ensure that any individual worker is only exposed to an uncomfortable temperature for a limited time.

The Display Screen Equipment (DSE) Regulations state that equipment at workstations shall not produce excess heat which could cause discomfort to operators or users (see UNISON’s separate guidance on the Health and Safety Six Pack or the DSE Regulations for further information).
Risk assessments carried out under the Manual Handling Operations Regulations (MHOR) require employers to take account of risks from various factors when manual handling, including hot or humid conditions (see UNISON’s separate guidance on the Health and Safety Six Pack or the MHOR for further information).

Negotiating advice

Branches should negotiate agreements on temperature with their employers. They should however, first identify the problems. This can be done by:

• surveying members;
• asking members to check and report thermometer readings in their workplace;
• ensuring that heating and cooling systems are included in workplace inspections;
• checking accident books.

Any joint agreement sought with the employer could include:

• Developing a policy for extreme weather events.
• Consider a minimum and maximum workplace temperature.
• A definition of what is meant by ‘reasonable and adequate’ when considering steps to be taken, both short term and long term, taking into account: the building, the number of people, the equipment used, and the work undertaken.
• A planned response to sudden changes in the weather.
• What will happen when the minimum or maximum temperatures are not maintained.
• Relaxing dress and uniform codes in the summer and/or improving the quality of the materials used.
• Extra breaks for night shift workers who may be suffering from lack of sleep during the day and subsequent fatigue during heatwaves.
• Redesigning work areas.
• Allowing staff to be more flexible in their working arrangements.
• Making workplace adjustments for staff who may be more vulnerable to extremes of heat or cold.
• Consider approaches which ensure that workers have a voice in a just transition to net zero carbon emissions commitments.

Health and safety representatives should ensure that their employer has carried out an adequate risk assessment and taken measures of control to ensure that no worker suffers from heat or sunstroke, excess of sun exposure, dehydration, or heat stress; or from excessive exposure to the cold.

Legal disclaimer 

The information contained within this article is not a complete or final statement of the law and is based on the laws of England, Wales, Scotland and Northern Ireland. 

While UNISON has sought to ensure that the information is accurate and up to date, it is not responsible and will not be held liable for any inaccuracies and their consequences, including any loss arising from relying on this information. If you are a UNISON member with a legal problem, please contact your branch or region as soon as possible for advice, or for non-employment matters call UNISONdirect.