Map shows how hot the weather has to be before it is officially a heatwave in the UK – Bundlezy

Map shows how hot the weather has to be before it is officially a heatwave in the UK

Two people relaxing on deck chairs in the warm sunshine in Green Park, London.
Soaking up the sun in Green Park, London (Picture: Amer Ghazzal/Shutterstock)

It’s time to dig out the SPF and stay hydrated as UK temperatures soar for the second time in two weeks.

Forecasters predict London and the south of England could reach up to 28°C on Friday, before rising to 30°C on Saturday and 31°C on Sunday.

It’s all thanks to a heatwave which is already developing across western Europe.

The UK Health Security Agency (UKHSA) has issued an amber heat health alert, which came into effect this morning and is in place until 6pm on Tuesday.

While the word ‘heatwave’ can get bandied around as soon as the sun starts to come out in the UK, there are certain thresholds that must be met before a heatwave is actually declared.

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The temperature that must be reached for a heatwave to be announced is different depending on what area of the UK you’re in, meaning parts of the country can be in a heatwave while others aren’t.

Is there officially going to be a heatwave this week?

Some Britons are set to bask in a heatwave this week.

The Met Office defines the weather event as when temperatures meet or exceed the threshold for a specific area for three consecutive days.

A graphic showing hot how it has to be in different areas of the UK, for three consecutive days, to count as a heatwave. In London, this is 28 degrees Celsius. In cities such as Bristol, Cardiff and Manchester the thresholds are 27, 26 and 25 degrees Celsius, respectively.
Maps show how hot it has to be in different areas of the UK, for three consecutive days, to count as a heatwave (Picture: Metro)

As shown in the map above, in London, this is 28°C, whereas in cities including Bristol, Cardiff and Manchester, the threshold is 27°C, 26°C and 25°C, respectively.

The Met Office is warning that this weekend and early next week are likely to bring the highest temperatures of 2025 so far.

Deputy chief meteorologist Mike Silverstone said: ‘Higher temperatures building over the weekend and into early next week will bring particularly warm, hot or even very hot conditions for some.

‘By the weekend, an area of high pressure will be intensifying and dominating the UK forecast.

‘Conditions will be hottest in the south and east while areas further north and northwest will be relatively cooler.

‘Monday could see temperatures reach around 34°C in some parts, though we will be able to be more precise closer to the time.’

How long will the hot weather last?

The burst of heat is expected to peak this weekend before easing early next week.

There is uncertainty in how quickly it will cool, with some models predicting temperatures in the mid-30s by Monday.

Mike added: ‘The heat is most likely to gradually relent from the west on Tuesday and into Wednesday, with a return towards more average temperatures for the second half of next week.

Which areas of the UK will see the warmest weather?

weather temperature maps - metro graphics
Temperatures are likely to peak in London and the south east of England (Picture: Metro Graphics)

The Met Office has warned the hottest temperatures across the weekend will be seen in the south east and East Anglia and more locally elsewhere in England and east Wales.

What is the hottest the UK has ever been?

The Met Office confirmed the UK’s record high temperature was 40.3°C. The mercury hits those heights in Lincolnshire in July 2022.

The extreme temperatures were recorded as the UK was sweltering in an unprecedented heatwave.

In that time, the previous UK record temperature of 38.7°C was provisionally met or exceeded in 46 places across the UK, while seven areas saw temperatures above 40°C.

Dr Mark McCarthy, from the National Climate Information Centre, told the Met Office in 2022 that without human-induced climate change, ‘it would be virtually impossible for temperatures in the UK to reach 40°C.’

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