The highest temperature on record in Wales has now risen to 37.1C in Hawarden, Flintshire, provisional Met Office figures show.
It's the second time the record has been broken today after 35.3C was recorded in Gogerddan, near Aberystwyth, earlier on Monday.
The previous record high of 35.2°C, recorded at Hawarden Bridge, Flintshire on 2nd August 1990.
The temperature record will need to be verified by the Met Office.
An amber weather warning for extreme heat is in place for all of Wales, covering Monday and Tuesday.
A red weather warning for heat was issued across parts of England.
The public have been urged not to travel unless necessary with conditions on public transport expected to be "uncomfortable".
The speed limit on rail lines has been limited to 90mph, reduced from 125mph, meaning journeys will take longer.
People have also been warned to keep pets and livestock cool.
Farmers at the Royal Welsh Show near Builth Wells in Powys, the UK's biggest agricultural event, are said to be taking measures to care for the around 8,000 animals attending.
The UK Government has declared a national emergency following the Met Office updating its weather warnings to red – meaning a risk to life – for large parts of England, including the West Midlands and North West England.
People are being urged to stay inside during the hottest points of the day, between 11am and 4pm, and wear sun cream, a hat, stay in the shade and keep hydrated with water.
Emergency services have also urged people to be cautious when cooling off and be cautious in the sun.
Recommended precautions include avoiding physical exercise, keeping to the shade and maintaining ventilation, drinking plenty of water and using in-date sun cream.
Water companies have been experiencing "unprecedented peak demand" amid the extreme heat.
People are being encouraged to "carefully consider" their water usage, and urged not to waste it in the high temperatures.