Heat waves are prolonged periods of excessively hot weather, relative to normal conditions, and are sometimes accompanied by high humidity.
While most of us welcome higher temperatures, heat waves can cause various health problems, especially for those with existing health issues.
If you are likely to be at particular risk, or care for people who could be at risk during a heat wave, it's important that you plan ahead - taking action in advance can help reduce the problems caused by this type of weather.
The main risks posed by a heat wave are:
- Dehydration (not having enough water);
- Overheating, which can make symptoms worse for people who already have problems with their heart or breathing; and
- Heat exhaustion and heatstroke.
A heat wave can affect anyone, but the most vulnerable people are:
- Older people, especially those over 75;
- Babies and young children;
- People with a serious chronic condition, especially heart or breathing problems;
- People with mobility problems - for example, people with 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; and
- People who are physically active - for example, manual workers or those doing sports.
If heat exhaustion is left untreated, heatstroke can develop, but it can also occur suddenly and without warning. Remember, heatstroke can kill. It can develop very suddenly, and rapidly lead to unconsciousness. If you suspect someone has heatstroke, call 999 immediately.
For more information on how to cope in hot weather visit the NHS Choices heatwave: how to cope in hot weather page.
To find out what the heat health watch plan is for your area see the Met Office heat-health watch page.