Since records began, only four days have been hotter than today in the UK.
The highest temperature ever recorded was on 19 July 2022 when temperatures at Coningsby, Lincolnshire, reached 40.3C. That marked the first and only day that readings above 40C have been seen in the UK.
Before that, the record was 38.7C at Cambridge Botanic Gardens on 25 July 2019.
Faversham in Kent reached 38.5C on 10 August 2003, while on 18 July 2022 a temperature of 38.2C occurred at Pitsford, Northamptonshire.
Amber warnings for “extreme heat” are in place for a swathe of England from London to Sheffield, parts of Cheshire and Greater Manchester, into Gloucestershire and Wiltshire in the South West and Shropshire and Herefordshire in the west.
Temperatures were also forecast reach 35C in Wales, where a drought has been declared across the whole country.
Meanwhile, a yellow thunderstorm warning is in place for Northern Ireland until 06:00 on Friday, while rain is forecast for much of Scotland.
In England, the extreme heat in this heatwave is now believed to have peaked, with cooler temperatures of 30-34C expected for the Midlands, East Anglia and much of southern England by Friday, ceding to 26C by Sunday.
More than 27 million people are facing water use restrictions, including hosepipe bans.
Thousands of homes in east London and Essex are still experiencing a complete water outage or low water pressure, almost a week after a series of pipes burst in South Woodford.
Thames Water has repeatedly apologised for the outage and said it expects to have supplies restored by Friday.
The heat is proving to be deadly, and A&E departments in England recorded their busiest period ever, with the record-breaking heat cited as a key factor.
In July, 2.49 million people attended emergency departments, and preliminary figures suggest there were more than 2,800 heat-related deaths in May and June – almost double the total for last year.
An ambulance technician said working in the heat was “vile”, while other healthcare workers have said they are “dripping with sweat from head to toe”.
Health Secretary Yvette Cooper said the figures show how much of an “additional burden is placed on the NHS during periods of extreme heat,” and said the NHS must plan for summer pressures in a similar way to winter.
A total of 1,017 wildfires have been recorded in England and Wales this year, according to data shared by the National Fire Chiefs Council (NFCC), which matches last year’s record.
In the New Forest, Hampshire, a team of 130 firefighters battled a wildfire on Thursday that has affected an area roughly the size of 230 football pitches, authorities said.
The UK is facing increasingly extreme conditions such as heatwaves, drought and wildfires fuelled by climate change.