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Home Topics Emergency Response Extreme weather events and natural disasters Heatwave Heatwave Questions and Answers

Heatwave Questions and Answers

Why is a heatwave a problem?

The main risks posed by a heatwave are:

  • Dehydration (not having enough water).
  • Overheating. Can make symptoms worse for people who already have problems with their heart or breathing. 
  • Heat exhaustion.
  • Heatstroke. Can make people very ill and can sometimes be fatal.

For more information on heat exhaustion and heatstroke, see External Links.


Who is at risk?

A heatwave can affect anyone, but the most vulnerable people are:

  • Older people, especially over 75 years.
  • Babies and young children.
  • People with a serious chronic condition, especially heart or breathing problems.
  • People with mobility problems, for example people who have Parkinson's disease or who have had a stroke. 
  • People with serious mental health problems.
  • People on certain medications, including those that affect sweating and temperature control.
  • People who misuse alcohol or drugs.
  • People who are physically active, for example labourers or those doing sports.


What is heat exhaustion?

Heat exhaustion occurs when the temperature of the inside of the body, which is known as the core temperature, rises to between 37-40°C (98.6-104°F). Heat exhaustion can develop after several days of exposure to high temperatures and inadequate or unbalanced replacement of fluids. Those most prone to heat exhaustion are elderly people, those with high blood pressure, and those working or exercising in a hot environment.

At that temperature, levels of water and salt in the body begin to drop leading to a range of symptoms such as nausea, feeling faint and heavy sweating.
Left untreated heat exhaustion can then progress to heatstroke.


What are the symptoms of heat exhaustion?

The symptoms of heat exhaustion can develop rapidly. Symptoms include:

  • your skin feels very hot and flushed,
  • heavy sweating,
  • dizziness,
  • fatigue,
  • nausea,
  • vomiting,
  • rapid heartbeat (tachycardia),
  • mental confusion and
  • decreased urine output and the colour of the urine is much darker than usual.


What is heatstroke?

Heat stroke is the most serious heat-related illness. It occurs when the body becomes unable to control its temperature: the body's temperature rises rapidly above 40C (104F), the sweating mechanism fails, and the body is unable to cool down. Body temperature may rise to 106°F or higher within 10 to 15 minutes and many of the important functions of the body will begin to stop working.

Heat stroke can cause death or permanent disability if emergency treatment is not provided.

Heatstroke is a medical emergency. Left untreated heatstroke can cause multiple organ failure, brain damage and death.


What are the symptoms of a heat stroke?

The symptoms of classic heatstroke can develop over the course of several days if you are spending prolonged time in a hot environment. While the symptoms of exertional heatstroke can develop rapidly, usually after a long period of physical activity.

Symptoms of heatstroke may vary but include:

  • high body temperature  - a temperature of or above 40°C (104°F) is a major sign of heatstroke,
  • red, hot skin and excessive sweating that then suddenly stops; if the body is unable to produce any more sweat this is a serious warning sign that they body has become over-heated and dehydrated,
  • rapid heartbeat (tachycardia),
  • hyperventilation, and
  • muscle cramps.

The extreme heat associated with heatstroke also affects the nervous system which in turn can cause additional symptoms such as:

  • mental confusion,
  • nausea,
  • lack of co-ordination,
  • seizures (fits),
  • restlessness or anxiety,
  • difficulties understanding or communicating with others,
  • hallucinations (seeing or hearing things that are not real),
  • loss of consciousness.

Heatstroke is a medical emergency. If you are concerned that you or somebody you know may be experiencing the symptoms of heatstroke you should immediately dial 999 and ask for an ambulance.


How can I reduce the risk and keep healthy?

The following advice applies to everybody when it comes to keeping cool and comfortable and reducing health risks. If you know or care for someone in one of the vulnerable categories above, you can also help them to follow this advice:

  • Avoid the heat. Stay out of the sun, and plan ahead so you don't go out between 11am and 3pm, the hottest part of the day.
  • Avoid excessive physical activity, or do it in the cooler ends of the day.
  • Keep rooms cool by using shade or reflective material external to the glass, or if not possible by closing pale-coloured curtains. Metal blinds and dark curtains can make the room hotter.
  • Keep the windows closed while the room is cooler than it is outside. If safe, open windows at night when the air is cooler.
  • Have cool baths or showers, and splash yourself with cool water.
  • Drink water or fruit juice regularly (avoid alcohol, tea or coffee).
  • Wear loose, cool clothing and a hat if you go outdoors.
  • Listen out for information on the radio or TV. A warning system is in place to issue alerts if a heat wave is likely. If alert level two is issued, there is a 60% chance that a heat wave will occur within the next few days. Alert level three is issued when a heat wave is happening.


How do I know if someone needs help?

If someone feels unwell, get them somewhere cool to rest. Give them plenty of fluids to drink. Cool the person as rapidly as possible, using whatever methods you can. For example, immerse the victim in a tub of cool water; place the person in a cool shower; spray the victim with cool water from a garden hose; sponge the person with cool water; or if the humidity is low, wrap the victim in a cool, wet sheet and fan him or her vigorously.
If symptoms such as breathlessness, chest pain, confusion, weakness, dizziness or cramps get worse or don't go away, seek medical help.

Heat exhaustion and heatstroke both require urgent treatment.

   Heat exhaustion Heatstroke 
  • headaches
  • dizziness
  • nausea and vomiting
  • muscle weakness or cramps
  • pale skin and
  • high temperature
  • headaches
  • nausea
  • intense thirst
  • sleepiness
  • hot, red, and dry skin
  • sudden rise in temperature
  • aggression, confusion, convulsions or loss of consciousness
 What to do
  • Move somewhere cool
  • Drink plenty of water or fruit juice
  • Take a lukewarm shower, or sponge yourself with cold water

CALL 999

Whilst you wait for the ambulance:

  • Move the person to somewhere cooler
  • Loosen clothes, sprinkle them with cool water or use a damp sheet/cloth
  • If conscious, give them water
  • Do not give them paracetamol or aspirin
 Sources of help

Check the weather forecast and any high temperature health warnings at the Met Office

Contact NHS Direct on 0845 4647 or NHS Direct for advice about heat exhaustion and heatstroke.

You can get advice on protecting your skin during hot weather from the Cancer Research UK SunSmart site campaign website