There have been warnings of further severe thunderstorms, flash floods and hail in parts of England and Wales on Wednesday night.
Flash flooding is predicted for Wales and the West Country
BBC forecasters say Wales and the West Country have a risk of flash floods and high winds.
Storms continued to hit parts of the country during Wednesday - affecting Salisbury Plain, east Wales and Thames Valley in particular.
But after the storms clear the weather is set to become much calmer.
At the start of the week temperatures reached over 31C (88F) in the south east of England.
But having been warned earlier to take care in the heat, people have now been advised to watch out for localised flooding from torrential downpours.
The Met Office has warned of the possibility of disrupted electricity supplies, and damage from large hailstones and strong gusty winds.
Rain stopped play for a time at Wimbledon, where the men's quarter-finals were taking place on Wednesday.
But BBC forecasters say that although there will be some storms on Thursday in the southern half of the country, they will not be as widespread or damaging.
The worst of the heat and humidity is expected to be over once after Wednesday night is over.
The storms caused severe disruption on the south coast rail route on Wednesday, with buses replacing trains between Brighton and Littlehampton after lightning in the Lancing area.
Signals were disrupted for more than an hour, with continuing delays for London-bound travellers.
Clean-up operations were also under way in the English Midlands after dozens of homes were affected by flash flooding.
The village of Albrighton, in Shropshire, was temporarily cut off when torrential rain forced the closure of several local roads.
In Leicestershire and Northamptonshire half an inch of rain fell in the space of one hour.
The Met Office's warnings, valid from 0900 to 1800 BST, cover the eastern counties, south-east England, the West Country and central southern England.
The government health warnings over the heatwave are still in place until Friday.
Despite the storms, most of Britain will continue to feel warm and humid with temperatures expected to peak at 27C (81F).
So far, NHS Direct has received about 2,500 additional calls per day, from people asking for advice on coping with the heat and reporting heat-related problems.
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