Warnings have been issued ahead of what's expected to be a scorcher on Friday (June 17), with temperatures expected to top 30C in Nottinghamshire, according to the Met Office. The forecast for Friday is cloudy in the morning before that clears and the sun shines through the afternoon, with temperatures reaching their peak at around 4pm.
It's expected to be warm until then, too, with sunny spells and highs of 24 forecast through Wednesday (June 15) and Thursday (June 16). The Met Office has issued a level two heat-health alert, which says: "Hot weather can be dangerous, especially for the very young or very old or those with chronic disease."
Southern parts of England have a level three heat-health alert, one of the highest out of an alert level of four. In Nottinghamshire on Friday, a very high pollen count is expected, with UV levels expected to be high too, and winds of up to 31mph.
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The highest temperature reached in the UK so far this year is 27.5C at Heathrow on May 17, with temperatures expected to reach 34C in southern parts of the UK. The Met Office says it is still relatively unusual for temperatures to reach this height in June.
Dan Rudman, deputy chief meteorologist at Met Office, said: "Temperatures will continue to rise as we go through the week, becoming well above-average by Friday when many parts of the southern half of the UK are likely to exceed 30C and may even reach 34C in some places. This is the first spell of hot weather this year and it is unusual for temperature to exceed these values in June.
"Many areas will also see some warm nights with minimum temperatures expected to be in the high teens or even low 20s for some overnight. The heat is a result of a mix of home-grown warming in the day due to high pressure, as well as a southerly airflow introducing some of the warm air from the continent to UK shores."
Agostinho Sousa, head of extreme events and health protection at the UK Health Security Agency, said: "Temperatures are forecast to reach 30C in some parts of the south on Friday and we want everyone to enjoy the hot weather safely when it arrives and be aware of good health advice for coping with warmer conditions. During periods of hot weather it is especially important to keep checking on those who are most vulnerable, such as older people and those with heart or lung conditions.
"Make sure to look out for signs of heat exhaustion and follow our simple health advice to beat the heat."
The highest recorded June temperature was on June 28 1976, when 35.6C was reached at Southampton Mayflower Park. The average June maximum temperature for the UK as a whole is 18C.
An Environment Agency spokesperson said: "There is a low-risk of drought for public water supplies this summer. However, further hot, dry weather could put pressure on some areas.
"Dry weather this spring has led to receding river flows and reservoir levels across central and south western England in particular. Early June rainfall has offered some relief with river flows improving compared to the end of May, however, a third of river flows remain below normal for the time of year.
"As always, we continue to work with water companies and wider stakeholders to closely monitor water resources and take action, where necessary. People should use water wisely and follow advice from their suppliers."
A cold front from the north introduces more uncertainty on how long the highest temperatures will hang on for Saturday, with areas to the southeast currently most likely to hold on to warmth the longest, although the extent of this is still being determined.
