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Summary for primary care

Supporting Vulnerable People Before and During Hot Weather


This new Guidelines summary covers the UK Health Security Agency (UKHSA)’s advice on caring for people most at risk during hot weather, including recommendations on the effects of heat on health, knowing who is at risk, treating heat-related illnesses, and considering medications that may increase risk to heat.

For a complete set of recommendations, refer to the full guideline. 

Reflecting on your Learnings

Reflection is important for continuous learning and development, and a critical part of the revalidation process for UK healthcare professionals. Click here to access the Guidelines Reflection Record.

Main Messages 

  • Reduce the risks associated with hot weather for those you care for by:
    • adapting individual care plans to respond to hot weather
    • having action plans in place tailored to the local context
    • knowing who is at risk
    • knowing how to treat heat-related illnesses
    • being alerted to increased cardiovascular and respiratory complications
    • considering medications that increase risk to heat
    • promoting environmental and behavioural changes that could reduce the risk of hot weather.

Heat and Health

  • Severe hot weather is dangerous to everyone. Heatwaves can happen suddenly, and rapid rises in temperature affect vulnerable people very rapidly and prove fatal. Climate change means dangerous hot weather is becoming more common in England
  • Deaths and morbidity from hot weather are preventable and require careful preparation. Plans need to be in place before high temperatures are forecast and should be ready before 1 June each year
  • During the summer, the UKHSA works with the Met Office to issue alerts when the weather is so hot that it has the potential to affect people’s health.

Who is at Risk?

  • In moderate hot weather, it is mainly individuals in the high-risk groups that are affected. But, during an extreme heatwave, fit and healthy people can also be affected
  • People adapt to heat via physiological responses (such as sweating) and behavioural changes (changing clothes). Individuals become at risk to heat when one or more of these mechanisms is limited, for example, by illness, frailty, or medication
  • Consider what:
    • the individual's risk factors are for being ill during hot weather
    • can be changed to protect them
  • An individual’s risk is related to a combination of factors relating to their health, behaviours, and environment
  • High-risk factors include:
    • older age (especially >65 years)
    • children (<5 years)
    • those living on their own and who may be unable to care for themselves or socially isolated
    • individuals that depend on others for routine activities
    • medical conditions, including cardiovascular, kidney, and respiratory conditions; diabetes; peripheral vascular disease; Parkinson’s disease; obesity; or severe mental illness
    • medications that potentially affect heart or kidney functions or an individual’s behaviour, cognition, or ability to sweat
    • behavioural limitations: for example, cognitive impairment (such as dementia), restricted mobility, or the use of alcohol or other recreational drugs
    • overexposure to heat: for example, living in a top-floor flat, being homeless, or outdoor occupations and activities.

The Effects of Heat on Health

  • During severe hot weather, there is a risk of developing heat exhaustion, heatstroke, and other heat-related illnesses, including respiratory and heart problems
  • The main causes of illness and death from hot weather are respiratory and cardiovascular diseases. Part of this risk may be attributable to air pollution, which can worsen in hot weather. Those with pre-existing lung or cardiovascular conditions should take extra care
  • Hot weather and dehydration increase the risk of infection and sepsis caused by Gram-negative bacteria, particularly Escherichia coli. The risk is greatest in individuals aged >65 years, emphasising the importance of ensuring adequate fluid intake in older people.

Heat-related Illnesses 

  • There is a spectrum of heat-related illnesses ranging from heat cramps, through heat exhaustion, to heatstroke. These are avoidable and preventable by early intervention and preparation.

Heat Cramps

  • Symptoms of heat cramps include:
    • painful muscular spasms caused by electrolyte imbalance, often following exercise
    • intense thirst with muscle cramps and a high heart rate
    • sweating preserved
    • normal cognitive state.

Heat Exhaustion

  • Symptoms of heat exhaustion include:
    • body temperature rising, but still capable of dissipating heat
    • appearing flushed, and sweaty, and complaining of feeling hot
    • mild cognitive dysfunction with mild confusion, irritability, anxiety; poor coordination may occur
  • Other signs of organ dysfunction may be present, including decreased urine output, headache, thirst, fainting, orthostatic hypotension, and nausea.


  • Heatstroke is a medical emergency and needs urgent management in hospital
  • Heatstroke can be classic, due to passive exposure to extreme heat, or exertional, from strenuous physical exercise
  • In both cases, the body loses the capacity to dissipate heat, and there is central nervous system impairment. Heatstroke commonly presents with hyperventilation, hypotension, and shock. The thermoregulatory centre may fail, so affected individuals may feel cold and dry to touch
  • The loss of ability to sweat is a late and severe sign of heatstroke. Multiple organ dysfunction and death can rapidly occur.
The World Health Organization's guideline, Public health advice on preventing health effects of heat, contains more guidance on the clinical management of mild and moderate heat-related illnesses and life-threatening heatstroke. 

Emergency Treatment of Heatstroke 

  • If someone has suspected heatstroke, call 999
  • While waiting for the ambulance:
    • take the person's temperature
    • if possible, move them somewhere cooler
    • cool them down as quickly as possible by spraying with cool water, and using a fan to maintain an air current if ambient temperature <35°C
    • place cold packs on neck, armpits, and groin
    • encourage them to drink cool fluids if they are conscious
    • do not give aspirin or paracetamol.

How to Prepare for Hot Weather

  • Preparation before hot weather is forecast is essential and plans should be agreed and communicated appropriately before 1 June each year
  • Make as much use as possible of existing care plans to assess which individuals are at particular risk, and to identify what extra help they might need. Where possible, involve their family and any informal carer in these arrangements
  • Action cards for providers can be found on GOV.UK.
For recommendations on how to keep buildings and resources cool, refer to the full guideline. 

How to Keep People Cool

  • As well as keeping indoor temperatures as cool as possible, consider the following to reduce individual’s risk:
    • move the most vulnerable to the coolest rooms (a cool room should ideally be <26°C)
    • reduce physical exertion, for example, reschedule physiotherapy to cooler times of the day
    • promote regular cool showers, baths, or body washes
    • advise wearing light, loose-fitting clothes that absorb sweat and prevent skin irritation
    • minimise sun exposure between the hours of 11.00 and 15.00
    • promote sunscreen use (further guidance can be found on NHS.UK)
    • sprinkle clothes with water regularly and splash cool water on their face, and the back of their neck
    • serve cold food, particularly salads, fruit, and ice lollies, which have high-water content
    • promote regular drinking, preferably water or fruit juice, and advise against alcohol use
    • monitor fluid intake, which can be done by monitoring body weight.

Consider Extra Care Needs 

  • Anyone in a high-risk category who is living alone is likely to need at least daily contact, whether by care workers, volunteers, or informal carers. Individuals at greater risk may need extra care and support
  • Check that:
    • extra care and support are available if needed
    • the person can contact the primary care team if one of their informal carers is unavailable
    • their care plan contains contact details for their GP, other care workers, and informal carers
    • there are adequate arrangements for food shopping and other essentials, to reduce having to go out in hot weather.

Medications with Increased Risk During Hot Weather

  • Some medications increase the risk of adverse health outcomes during hot weather. The degree of risk depends on the person’s lifestyle, health status, and their medications
  • The medications listed below are nonexhaustive, and serve as a prompt to consider action and assess the risks and benefits of any changes:
    • diuretics, especially loop diuretics, can lead to dehydration and electrolyte abnormalities
    • medications that interfere with cardiovascular responses, such as antihypertensives and antianginal drugs
    • medications that interfere with sweating, such as anticholinergics or beta blockers
    • drugs that cause diarrhoea or vomiting, such as colchicine, antibiotics, and opiates, which can lead to dehydration
    • medications that can impair renal function, such as antimicrobials, immunosuppressants, nonsteroidal anti-inflammatories, antiulcer agents, and chemotherapies
    • agents with levels affected by dehydration, such as lithium, digoxin, and antiepileptics
    • drugs that alter states of alertness, such as hypnotics, anxiolytics, and analgesics
    • medications that can interfere with central nervous system thermoregulation, such as neuroleptics and serotoninergic agonists
    • drugs that increase basal metabolic rate, such as thyroxine.

Storage of Medications

  • Most medicines should be kept <25°C, so they should be stored somewhere cool, dry, out of direct sunlight, and away from windowsills. Medicines should only be stored in the fridge if specified. The NHS Specialist Pharmacy Service has further guidance.

Further Information

For more information on Heat-Health Alerts, NHS advice, and air quality, refer to the full guideline.