A heatwave is coming – but don’t expect it to last

Beach
Sunseekers have been warned to be careful in temperatures that could reach 86F (30C) at the beginning of the week - Graham Hunt/BNPS

Britain will sizzle in three days of summer this week before thunder and rain puts a dampener on the weather just in time for Glastonbury.

Temperatures could reach 86F (30C) in some parts of the country, triggering a yellow health warning between Monday and Thursday from the UK Health Security Agency (UKHSA) and the Met Office.

However, thunderstorms and rain are forecast in the south-west by midweek, so Glastonbury festival goers could be pitching their tents in muddy fields at Worthy Farm in Somerset.

The Met Office said temperatures would peak on Wednesday before a “breakdown” with heavy showers and thunderstorms. The most persistent rain is likely in the west or south-west.

A spokesman said: “A largely settled start to the week will see plenty of dry and fine weather, feeling rather hot at times.

“By the weekend cooler, changeable conditions become more likely.”

The potential mini-heatwave has led to emergency services issuing warnings with people urged to stay out of the water to avoid fatal cold water shock.

The RNLI, the National Coastwatch Institution and emergency services across the UK warned that jumping into water to cool off on a hot day can trigger an involuntary gasp of breath that can lead to drowning.

Accidentally inhaling just half a pint of water can be fatal, experts warned, and said the phenomenon could affect even the strongest and most confident swimmers.

‘Don’t swim in open water’

Cold water shock occurs in water below 59F (15C). The average sea temperature around the UK and Ireland is 53.6F (12C) while inland waters such as lakes, rivers, lochs and reservoirs can be colder even in the summer.

A spokesman for Derbyshire Fire & Rescue Service said: “When the weather is hot, don’t be tempted to swim in open water.

“It can look inviting but has strong currents, hidden dangers, is cold and causes cold water shock.”

The yellow heat health alert has been issued for all of England except the north-east, as temperatures look likely to soar past 86F (30C), particularly in the south.

The UKHSA has warned of an “increase in risk of mortality among vulnerable individuals and increased potential for indoor environments to become very warm”.

Liam Esslick, a meteorologist at the Met Office, said: “My advice to people would be by all means go out and enjoy. They have been waiting for summer.

“But UV levels are going to be high and the sun will be very intense. Wear protection like sun cream, stay hydrated and try to get some shade in the midday sun. People sensitive to the sun should take particular precautions.”

The London Ambulance Service warned that heat can make pre-existing conditions worse and advised people to carry medication.

The Met Office advises keeping out of the sun 11am to 3pm when the UV ways are strongest, walking in the shade and wearing a wide-brimmed hat.

Physical exertion should be avoided in the hottest parts of the day along with alcohol and carry water when travelling.

During the hottest days householders are advised to close curtains, avoid heat-generating appliances and promote airflow through cross-ventilation and fans.