A heat health warning has been issued for parts of the UK including southern England, as parts of Dorset could see the hottest day of the year on Friday.

Temperatures are expected to reach the high 20s and possibly nudge into the 30s on Friday, forecasters have predicted.

And now, the Met Office, with the UK Health Security Agency have issued a warning for parts of the country.

The level three warning covers the south, south east and east of England, with the south west under a level two warning.

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What does it say?

The warning says there is a 90 per cent probability of Heat-Health Alert criteria being met between 0000 on Friday and 0000 on Sunday in parts of England.

There is high confidence for temperatures to rise significantly through the second half of this week, becoming hot or very hot in central and southern areas.

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The peak of the heat is expected on Friday, with temperatures likely to reach into the low to mid-30s across large parts of central and southern England.

Another warm night is expected in similar parts on Friday night before cooler and fresher conditions arrive during Saturday.

A spokesperson said: "There remains uncertainty in regards to the speed of progression of cooler conditions arriving from the north and west over the weekend.

"A slower outcome may allow for the very warm or hot conditions to persist across far southern areas on Saturday, before a more definitive return to more seasonable temperatures for all regions of England by Sunday."

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Is this likely to change?

An update will be issued when the alert level changes in any region, the statement says.

How are these alerts triggered?

They are triggered when the Met Office confirms threshold temperatures for one or more regions have been reached for one day and the following night and the forecast for the next day has a greater than 90 per cent confidence level that the day threshold temperature will be met.

What's the advice for those living under a level three warning?

  • Look out for others, especially older people, young children and babies and those with underlying health conditions.
  • Close curtains on rooms that face the sun to keep indoor spaces cooler and remember it may be cooler outdoors than indoors.
  • Drink plenty of fluids and avoid excess alcohol, dress appropriately for the weather and slow down when it is hot.