Chertsey in Surrey reported a high temperature of 30C (86F).
According to the weather service, this is the highest temperature to have hit the UK since September 10 of last year.
The highest recorded temperature in Winterbourne, Gloucestershire, was 28.7C; in Pershore, Worcestershire, and Usk, Monmouthshire, it was 28C and 27C, respectively.
The Met Office said that Wednesday might see even higher temperatures, with some regions seeing highs of 31C (87.8F).
For the majority of England, the UK Health Security Agency (UKHSA) has issued a yellow notice that will last until 5 p.m. on Thursday.
It has issued a warning that there may be “significant impacts” in the field of health and social services, as well as an increase in it.
Just before the weekend, things should drop off a bit, although the temperature will still be high.
The hot spell may turn into a heatwave, according to the Met Office, which happens when temperatures surpass a certain threshold – which varies depending on the region – for three consecutive days.
Worthy Farm’s temperatures are predicted to hit 27C on Wednesday, when the festival gates open. The rest of the weekend looks to be mostly sunny as well.
