Hundreds of schools have planned for at least partial closures and multiple train operators, including the UK’s largest, have warned people not to travel unless necessary as temperatures climb.
The top temperature recorded on Tuesday was 34.6C in Wisley, Surrey. Northern Ireland and Scotland saw their hottest days of the year, with temperatures reaching 28.1C and 29C respectively, while Wales hit a high of 32.2C.
The heatwave is expected to build further in the week, with temperatures of up to 39/40C forecast in England on Wednesday.
A red extreme heat warning has been issued across parts of England and Wales from Wednesday morning to Thursday evening, meaning there is a danger to life.
The UK had been forecast to experience its hottest June day on record on Tuesday, but this is no longer expected. Temperatures have been around 2C or 3C lower than predicted in south-east England after intense rainfall and flash flooding in some locations overnight.
More intense heat is still expected on Wednesday. A rare red extreme heat warning is in place from 09:00 BST to 21:00 Thursday, meaning there will be an exceptional spell of hot and humid weather in parts of south and central England and south Wales, according to the Met Office.
Spokesman Grahame Madge said it is possible the UK will see temperatures “higher than the 39C”.
The Dew Point – a measure of how humid the air is and how much water it is holding – could rise to 22C, which is far higher than the single figures recorded during the record-breaking heatwave of July 2022.
The humidity level will make temperatures feel five degrees warmer than the reading on the thermometer.
The forecaster warns there is risk of serious illness or danger to life in the impacted areas. Loss of power and other essential services such as water are also likely, due to a greater risk of failure of heat-sensitive systems and equipment.
Significantly more people are likely to visit coastal areas, lakes and rivers, leading to an increased risk of water safety incidents, it says.
A red heat health alert has also been issued by the UK Health Security Agency (UKHSA), from 01:00 on Wednesday until 23:00 on Thursday.
Prof Robin May, chief scientific officer at the UKHSA, said this was only the second time they had issued the red heat health warning – the last time in July 2022.
Speaking on BBC Radio 4’s Today programme, he said the warning “signals a very widespread threat” from the heat, including threats “to people who generally think of themselves as not being particularly threatened by heat”.
“Often we are warning about the vulnerable, the elderly, the young, but in this case we’re also warning otherwise healthy people in their prime of life to take very cautious steps, because this heat is going to be quite intense and can have very serious life threatening effects even in people who are completely fit,” he said.
Matthew Hopkins of the acute and ambulance network for the NHS alliance told the Today programme he expected demand on emergency services to increase over the next few days during the extremely hot weather period.
