sun, thermometer and wall

Health and Weather warnings for extreme heat

Within the UK over the past few years, we have seen changes in our typical weather patterns, including hotter temperatures in the summer months.

In July 2022, the UK recorded it hottest every day with the temperature reaching 40.3°C in England, many of the devolved nations also recorded their own new highest temperatures.

In response, the UK Health Security Agency (UKHSA) together with the Met office have produce a new Adverse Weather and Health Plan ‘Protecting health from weather related harm’.

In line with other weather warning systems in operation within the UK, an updated Heat-Health Alert (HHA) colour warning system will operate from the 1 June to 15 September each year.

  • Green (preparedness): No alert will be issued as the conditions are likely to have minimal impact and health; business as usual and summer/winter planning and preparedness activities.
  • Yellow (response): These alerts cover a range of situations. Yellow alerts may be issued during periods of heat/cold which would be unlikely to impact most people, but could impact those who are particularly vulnerable.
  • Amber (enhanced response): An amber alert indicates that weather impacts are likely to be felt across the whole health service, with potential for the whole population to be at risk. Non-health sectors may also start to observe impacts and amore significant coordinated response may be required.
  • Red (emergency response): A red alert indicates significant risk to life for even the healthy population.
(Reproduced from UKHSA User guide-New impact-based Weather-Health Alerting System)

These alerts are intended to provide information to those delivering health and social care services, as well as other businesses and the public.  This is to ensure preparations and changes to business operations can be planned and implemented.

So your employer should be monitoring these alerts and discussing the potential health and safety impacts to workers that may arise with health and safety reps.

This is because our bodies work hard to try and keep us comfortable because it can only take a few degrees change in our core temperature for us to become unwell.

Children under 4 years old, those with underlying health conditions, people who are pregnant and the elderly are more at risk of health issues from becoming too hot or too cold.

As the weather and temperatures vary across the UK, as with other weather warnings, alerts may be based on a regional rather than a national forecast. So different regions may have different alert levels.

The Met office may also issue National Severe Weather Warning Service (NSWWS) alerts for extreme heat in areas where temperatures are predicted to reach the thresholds shown below.

Reproduction of Figure 3.2: Local threshold temperatures within the Heatwave Plan for England: Protecting health and reducing harm from hot weather

Reproduction of Figure 3.2: Local threshold temperatures within the Heatwave Plan for England: Protecting health and reducing harm from hot weather

Devolved nations have their own threshold action levels, members living or working in those location should refer to the advice issued by the devolved administrations.

Cymru /Wales

Northern Ireland


What additional risk does extremely hot weather present?

Three of the biggest risks to health during extremely hot conditions are

Heat Exhaustion


Ultraviolet (UV) Rays

What should my employer be doing if Yellow, Amber or Red warnings for extreme heat are issued in the area I live or work?

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.

All employers are required to undertake risk assessments in relation to both the work being done and the environment in which that work is being carried out. Then put in place measures to reduce the risk of harm to their employees.  If something changes, for example a risk of extreme temperatures, they need to review those risk assessments and if necessary, take further steps to reduce possible harm.

Employers also need to take into account and act to protect staff who could be particularly vulnerable to the heat, at it would be appropriate for individual risk assessments to be undertaken in the event of any alert.

As UNISON members work delivering services in both the public and private sector across the whole of 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.

Below is some general advice on what we would expect employers to be doing and considering.

Do you need to be in the workplace?

Employers should be considering allowing employees to work from home wherever possible. This is because their responsibilities don’t start and stop at their front door. People commuting in Amber and Red warning areas are at significant risk of experiencing travel problem, with delays on roads and road closures, delays and cancellations to rail and air travel, which could cause people to suffer from heat exhaustion.

Where working from home is not possible, Employers should be carrying out a risk assessment which should considered the points below

Review the type of work being carried out

Employers should consider wherever possible avoiding work which requires strenuously activity, and where this is not possible, reducing the period of time it is done for,  insuring plenty of breaks and opportunities for to drink plenty of fresh cool water.

Workplace ventilation and thermal comfort

Ensuring good ventilation remains vital to help to reduce the transmission of SARS-CoV-2  the virus which causes Covid 19, with cases number on the increase employers still need to be thinking about protecting workers from this.

Oscillating fans can help with airflow, however where room temperatures are over 30oC, they may not help with cooling to prevent heat-related illness and may in fact worsen dehydration. The use and positioning of fans should also consider the transmission risk mentioned above.

Whilst there is currently no maximum workplace temperature, the law does state that;

“During working hours, the temperature in all workplaces inside buildings shall be reasonable”

So employers need to take all reasonable steps to achieve a temperature which is as close as possible to comfortable

UNISON supports the TUC’s call for a specific legal maximum temperature for indoor work of 30°C; or 27°C where the work is strenuous.

However, this proposed maximum would be intended to be the absolute maximum, so regular indoor work at or just below 30°C (or 27°C as applicable) would not be acceptable, and that employers should attempt to reduce temperatures if they went above 24°C or workers felt uncomfortable.  The World Health Organisation recommends 24°C as the maximum temperature for working in comfort.

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.

The Health and Safety Executive (HSE) have summed this up in the following way…

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


Personal protective equipment (PPE)

The need for personal protective equipment (PPE) will have followed a risk assessment and identified that all other means of reducing the risks to the individual have been eliminated but a level of risk still remains, so PPE is the last (not first) resort to protecting an individual.

The use of some types of PPE in hot outdoor / indoor environments (such as overalls, mask, respirators, aprons, hoods etc) increases the risk of the body not being able to cool itself and maintaining a healthy temperature (heat stress). This can cause heat exhaustion and if action is not taken lead to heat stroke.

If your work requires the use of PPE, we would expect employers to have review the risk assessment for the activity that requires PPE and consider avoiding this type of work in areas where is not possible to ensure a cool working environment.

Where the work needs to continue, and PPE is required we would be expecting employers to operate in the following way

  • Reducing the amount of time spent undertaking tasks in PPE by rotating staff out if the work / task needs to continue
  • Providing more frequent breaks in between the use of PPE
  • Trying to use single use PPE which is changed regularly to prevent sweat saturation and ensuring access to more changes of workwear
  • Make staff aware of the signs of heat exhaustion and dehydration
  • Operating a buddying system where staff regularly check on one another for signs of heat stress like confusion, changes in completion or looking clammy, increased rates of breathing (whilst at rest or not undertaking vigorous activity)

Outdoor workers

Those working outdoors need extra measures to protect them, both from UV radiation and heat stress. Therefore employers need to review their risk assessment and make employees aware of changes

(In Amber warning areas)

Work activities should be reduced and planned to take place at cooler times of the day (before 11 am and after 3pm), sun cream with a high UV factor should be provided free of charge, increased breaks out of the sun and free access to fresh cool water.

(In Red warning areas)

Only activities which are absolutely critical should be undertaken, [following that advice for Amber areas] but significantly limiting any work during 11am-3pm, employers might consider asking employees to undertake temporary duties out of the sun, provided they have received the appropriate training to be able to do that work safely.

Workers who are pregnant

Employers are already required by law to undertake individual risk assessments once an employee has informed them they are pregnant. We would expect employers to review this risk assessment in light of the Amber and Red warning for extreme heat.

The review should take account of the fact that workers who are pregnant are more at risk of experiencing heat exhaustion and at lower temperatures. Therefore, additional steps should be considered to reduce the risks and could include

  • Working from home where possible
  • Reducing shift length, start and finish times so you are not travelling in the hottest parts of the day
  • Staying well hydrated and having increased rest breaks
  • Temporary change of working duties

If you have any none medically urgent questions about the impact of the heat on your pregnancy you should discuss this with your midwife, contact your GP or call NHS 111

Those with existing health conditions

Where employers are aware someone has an existing health condition, once an alert has been issued, managers should be discussing with those employees how the extreme heat might affect either their condition or medication used.  We would encourage an individual risk assessment to be carried out, and for employers to consider what additional reasonable adjustment(s) could be provided.

If you feel you are being put at risk it is crucial to get advice and discuss the situation with your UNISON representative. Contact your branch and if needed you can seek advice from our regional office or legal team.

More guidance for Health and Safety reps on Temperature at Work

UKHSA and Met Office Service

It is aimed at health and social care professionals and any with a role in reducing the harm extended periods of hot weather can have on health. Individuals in England can sign up to receive alerts or access the alert dash board via the links below

Heat-health Alert service sign up link

Heat-health Alert dashboard

UKHSA advice for public services

The UKHSA has produced guidance to assist professionals in protecting vulnerable people from the health impacts of severe heat in England. (devolved nations may issue their own of reference these)

Social care managers, staff, and carers

Healthcare professionals

Supporting people who are homeless and sleeping rough

Looking after children and those in early years settings during heatwaves: for teachers and professionals

The signs of heat exhaustion include:

  • a headache
  • dizziness and confusion
  • loss of appetite and feeling sick
  • excessive sweating and pale, clammy skin
  • cramps in the arms, legs and stomach
  • fast breathing or pulse
  • a high temperature of 38C or above
  • being very thirsty

The symptoms are often the same in adults and children, although children may become floppy and sleepy.

If someone is showing signs of heat exhaustion, they need to be cooled down.

Call 999 if:

You or someone else have signs of heatstroke including:

  • fast breathing or shortness of breath
  • a fit (seizure)
  • loss of consciousness
  • not responsive

Heatstroke can be very serious if not treated quickly.

Put the person in the recovery position if they lose consciousness while you’re waiting for help.

Symptoms of dehydration in adults and children include:

  • feeling thirsty
  • dark yellow and strong-smelling pee
  • feeling dizzy or lightheaded
  • feeling tired
  • a dry mouth, lips and eyes
  • peeing little, and fewer than 4 times a day

Call 999 or go to A&E if:

  • you’re feeling unusually tired
  • you’re confused and disorientated
  • any dizziness when you stand up does not go away
  • you have not peed all day
  • your pulse is weak or rapid
  • you have fits (seizures)

These can be signs of serious dehydration that need urgent treatment.