Most of us welcome hot weather, but when it's too hot for too long, there are health risks. If a heatwave hits this summer, make sure the hot weather does not harm you or anyone you know.

Why is a heatwave a problem?

The main risks posed by a heatwave are: 

• not having enough water - Dehydration
• overheating, which can make symptoms worse for people who already have problems with their heart or breathing
• Heat Exhaustion and Heatstroke

Who's most at risk?

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

• older people, especially those over 75
• babies and young children
• people with a serious long-term 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 medicines, 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

Level 1 alert: be prepared

The Meteorological Office has a warning system that issues alerts if a heatwave is likely.

Level 1 is the minimum alert and is in place from 1 June until 15 September, which is the period that heatwave alerts are likely to be raised.

Although you do not have to do anything during a level 1 alert, it's advisable to be aware of what to do if the alert level is raised.

Knowing how to keep cool during long periods of hot weather can help save lives.

Public Health England (PHE) has advice on how to stay safe during a heatwave (PDF, 417kb).

Level 2 alert: heatwave is forecast

The Met Office raises an alert if there's a high chance that an average temperature of 30C by day and 15C overnight will occur over the next 2 to 3 days.

These temperatures can have a significant effect on people's health if they last for at least 2 days and the night in between.

Although you do not need to take any immediate action, follow these steps in preparation:

• Stay tuned to the weather forecast on the radio, TV or social media, or the Met Office.
• If you're planning to travel, check the forecast at your destination.
• Learn how to keep cool at home with the beat the heat checklist (PDF, 193kb).

Level 3 alert: when a heatwave is happening

This alert is triggered when the Met Office confirms there will be heatwave temperatures in at least 1 region.

Follow the instructions for a level 2 alert.

The following tips apply to everybody when it comes to keeping cool and comfortable, and reducing health risks.

Tips for coping in hot weather

• Shut windows and pull down the shades when it's hotter outside. You can open the windows for ventilation when it's cooler.
• Avoid the heat: stay out of the sun and do not go out between 11am and 3pm (the hottest part of the day) if you're vulnerable to the effects of heat.
• Keep rooms cool by using shades or reflective material outside the windows. If this is not possible, use light-coloured curtains and keep them closed (metallic blinds and dark curtains can make the room hotter).
• Have cool baths or showers, and splash yourself with cool water.
• Drink plenty of fluids and avoid excess alcohol. Water, lower fat milks and tea and coffee are good options. You can also drink fruit juice, smoothies and soft drinks, but they can be high in sugar. Limit fruit juice or smoothies to a combined total of 150ml a day, and choose diet or sugar-free soft drinks.
• Listen to alerts on the radio, TV and social media about keeping cool. 
• Plan ahead to make sure you have enough supplies, such as food, water and any medicines you need.
• Identify the coolest room in the house so you know where to go to keep cool.
• Wear loose, cool clothing, and a hat and sunglasses if you go outdoors.
• Check up on friends, relatives and neighbours who may be less able to look after themselves.

If you have concerns about an uncomfortably hot house that's affecting your health or someone else's, get medical advice.

You can also get help from the environmental health office at your local authority. They can inspect a home for hazards to health, including excess heat.

Level 4 alert: severe heatwave

This is the highest heatwave alert in Britain. It's raised when a heatwave is severe, prolonged, or both, and is an emergency situation.

At level 4, the health risks from a heatwave can affect fit and healthy people, and not just those in high-risk groups.

These groups include the elderly, the very young and people with long-term medical conditions.

Follow the information given above for a level 3 alert. Check that anyone around you who's in a high-risk group is coping with the heat.