Hot weather and heatwaves

Who heat harms, what it does to water, power and transport, the difference between an Extreme Heat warning and a Heat Health Alert, and how to keep a home cool.

Weather

What it is

Anyone can become unwell if they get too hot, through overheating, dehydration, heat exhaustion and heatstroke. Be Ready says hot weather also strains water and energy networks, road and rail, and the health and fire services, which can mean power cuts, water restrictions and transport disruption. In July 2022 temperatures in parts of England passed 40 degrees Celsius for the first time.

The people most at risk are older adults, babies and young children, pregnant people, people with heart and breathing problems, dementia, diabetes, kidney disease, Parkinson's disease or mobility problems, people who are physically active outdoors, people who are homeless, people who live alone, and people in top-floor flats or homes with restricted windows.

What it does to a home

Rooms facing the sun heat up and stay hot. Be Ready's advice is to shade and close windows and curtains by day and open them when the air is cooler. It may be cooler in the shade outside or in a public building such as a library, place of worship or supermarket, if you can get there without putting yourself at risk. Small closed spaces such as parked cars become dangerous very quickly. Road surfaces can be damaged by heat and rail speed restrictions cause delays. Hot weather can bring a power cut or restrictions on the water supply.

Who warns you

The Met Office guide separates three things. An Extreme Heat Warning is an impact-based warning issued through the National Severe Weather Warning Service, up to seven days ahead, coloured yellow, amber or red by impact and likelihood. A Heat Health Alert is an England-only service on the effect of prolonged heat on public health, especially for people with long-term conditions. A heatwave is a threshold-based meteorological definition used for consistent messaging. Be Ready links the Heat Health Alerts on the UK Health Security Agency dashboard.

If you are worried about someone's health, contact a pharmacist, GP or NHS 111. The NHS publishes advice on coping in a heatwave, on sunscreen and sun safety, and on keeping a baby safe in the sun. The Royal Life Saving Society publishes summer water safety advice for swimmers.

How the government assesses it

The National Risk Register 2025 says climate change has made extreme heat more likely and the trend will continue. Its reasonable worst case is five consecutive days above 35 degrees Celsius affecting 50 to 70 per cent of the UK population, approaching or passing 40 in parts of south-eastern, eastern or central England. It expects excess deaths above a normal summer, disruption to transport, supply chains, power and water, and other hazards arriving with or straight after the heat, including flooding from thunderstorms, poor air quality, drought and wildfires. UKHSA's Adverse Weather and Health Plan brings together the former Heatwave Plan for England, first published in 2004, and the Cold Weather Plan.

Where to look

Met Office warnings, hot weather guidance and WeatherReady at metoffice.gov.uk.
Heat Health Alerts at ukhsa-dashboard.data.gov.uk/weather-health-alerts/heat.
Beat the Heat advice and the keep cool at home checklist on gov.uk.
Related pages: droughts, wildfires, poor air quality and pollution.

Before

Read the NHS page on heat exhaustion and heatstroke. Heat exhaustion usually passes if the person cools within 30 minutes. Heatstroke is an emergency.
If you know someone at greater risk, make sure they know what to do and offer practical help such as stocking up on water or medication.
If your home overheats, for example a top-floor flat or one with windows that barely open, ask your council, letting agent or Citizens Advice what help exists.
Consider external shutters or awnings, internal blinds, or plants outside south-facing windows.
Before a hot spell, check the car's tyres, fluids, battery and air conditioning, and pack water in case of a breakdown or long queue.

During

Check the forecast, any Extreme Heat warning and any Heat Health Alert for your area, and act on the advice.
Turn the heating off and check fridges, freezers and fans are working.
Drink plenty. Take a refillable water bottle when you go out.
Keep out of the sun between 11am and 3pm, wear loose light-coloured clothing, a wide-brimmed hat and sunglasses, and apply sunscreen generously and often.
Shade and close windows and curtains in rooms facing the sun, and open windows when the air outside is cooler, such as at night.
Never leave babies, children, older adults or pets alone in a stationary car. Allow extra time for journeys and follow Do Not Travel warnings.

After

If someone's heat exhaustion has not eased within 30 minutes of cooling down, treat it as heatstroke and as an emergency.
The National Risk Register says flooding from thunderstorms, poor air quality, drought and wildfires are very likely to arrive with or just after a heatwave.
Use the Beat the Heat keep cool at home checklist on gov.uk to see whether your home is at risk of overheating and how to reduce it.

Sources

Last updated 29 October 2026. Reviewed 29 October 2026