The hot weather is set to continue into August weather experts predict.
The Met Office predicts less humidity in the next few days but says the heat will soon return. This July is already on target to be the hottest on record.
The heat has been causing problems across the UK, with high demand for air conditioning contributing to power cuts in London's Soho.
In Northumberland, seven Army cadets on exercise fell ill due to the heat and other parts were hit by violent storms.
Statistically, August tends to be hotter than July.
The hottest July day since records began was recorded in Wisley, Surrey, on July 19, when the temperature reached 36.5C (97.7F).
Other parts of the UK have also reached peaks, with July records of 30.8C in Belfast and 34.2C in Penhow, South Wales.
But so far the record for the highest temperature in the UK - 38.5C (101.3F) recorded in Faversham, Kent, on 1 August, 2003 - has yet to be broken.
July may yet break another record, for the number of sunshine hours - 266 compared to a long-term average of 201 hours.
The hot weather has taken its toll on people and businesses.
Four Sandhurst army cadets had to be airlifted to hospital after suffering "heat-related injuries" during an outdoor training exercise in Otterburn, Northumberland on Thursday.
They were taken to Newcastle's General Hospital as a precautionary measure, after training in full chemical suits, the Ministry of Defence confirmed.
And shops and offices in Soho, central London, were asked to conserve energy by switching off air-conditioning after a power failure in the area.
A series of faults had affected power distribution and the hot weather had added to the problem with extra demand for air-conditioning.
Energy supply was rationed, with rolling power cuts in Soho.
Meanwhile, the Midlands, East Anglia and south-east England were battered by heavy rain, as soaring temperatures led to thunderstorms and lightning.
Despite the storms, temperatures remained high, with the south-east of England staying hot and humid.
Some families in East Anglia were mopping up on Thursday after electric storms caused flooding.
Police in Cambridgeshire said had been problems in and around Melbourn and March following torrential rain late on Wednesday.
A spokesman said flash floods were reported to have left one road in Melbourn under 3ft of water and that parts of March police station were flooded.
The emergency services said a house near Diss, Norfolk, caught fire after being hit by lightning.
No-one was hurt but the blaze caused severe damage.
And a 70-year-old woman was left shaken but unhurt when her Southampton home was hit by lightning at 10pm on Wednesday.
A total of 12 firefighters tackled the blaze, which destroyed the roof, gutted the loft and caused extensive smoke and water damage to the ground floor, according to a Hampshire Fire and Rescue Service spokesman.