Engineers are enduring the searing temperatures today to reconnect hundreds of householders hit by a power cut during a lightning storm.
The thunderstorm which hit the north-east of England during yesterday's record-breaking temperatures left 40,000 homes without electricity in parts of North Yorkshire, County Durham, Tyne and Wear and Northumberland.
Northern Powergrid said power had been restored to 32,500 of its customers by 7pm and work was continuing to make sure the rest were connected by this afternoon.
A spokeswoman said: "We're sorry for the inconvenience caused to our customers as a result of the storm damaging our network and we thank them for their patience while our team works hard to carry out the necessary repairs."
The storm was one of a number of spectacular lightning shows that swept across northern England and Scotland in the wake of what was for many places the hottest July day on record.
Scores of motorists pulled over to watch last night as a storm moved up The Pennines.
In Sheffield, weather-watchers drove out of the city to witness the huge cloud which silently flashed with almost continuous lightning but with no thunder and no rain.
In the village of Worrall, Rick Taylor, said: "I've not anything like this before, It's amazing. It's exactly like that scene in Close Encounters of the Third Kind when the spaceship is approaching."
The light show gradually worked its way north, with people using social media to chart its progress through Huddersfield and then on to Leeds, Bradford and the Yorkshire Dales.
Leeds North West MP Greg Mulholland said on Twitter: "What an amazing spectacle of nature. I hope it's not like Day of the Triffids."
Felicity Grace posted: "The entire population of Bradford aged 18 and below will be falling asleep in school tomorrow because of this lightning."
Elsewhere, hailstones as big as golf balls were reported to have caused damage in parts of North Yorkshire and County Durham and the Tornado and Storm Research Organisation even issued a tornado warning for parts of the Midlands.
Its statement said: "Shear is sufficient for organised severe thunderstorms including supercells, capable of large hail, damaging winds, and perhaps isolated tornadoes."
Forecasters said there would be some respite today from the soaring temperatures yesterday, which reached a maximum recorded temperature of 36.7C (98F) and caused roads to melt and rail service cancellations.
But parts of south-east England could still see the mercury rise to around 26C (79F) today and the heatwave looks set to continue into the weekend.
Western parts of England and Wales could see heavy showers during the day while hail and lightning struck the North and Scotland overnight, according to forecasters.
MeteoGroup's Nick Prebble said: "Temperatures will be suppressed today, about 10C lower than yesterday with highs of 25C or 26C. It will be noticeably cooler but still warm.
"Friday will likely stay nice and dry across most places and temperatures will be a little warmer, around 27C or 28C, although there will be some unsettled weather Friday night with more thunderstorms, possibly in the south west of England.
"Looking into the weekend, it could top 30C again on Saturday in the South East and London and temperatures will be above average elsewhere too, going in to Sunday."
Moderate levels of air pollution are expected to remain in the southern and eastern areas of England throughout today and Friday before subsiding over the weekend, according to the Department for Environment, Food and Rural Affairs (Defra)
Earlier it had warned those vulnerable to the effects of pollution to be cautious as the high temperatures caused pollution levels to spike.
Urgent health warnings were issued in response to the heatwave yesterday and paramedics dealt with a surge in calls amid fears the hot weather could result in deaths.
The London Ambulance Service said it had seen call-outs to people fainting increase by more than a third (35%) compared with the same day last week, and a 28% hike in overall calls during the period.
Players at Wimbledon sweltered in the searing heat on courts on the tournament's hottest ever day.
The Met Office said temperatures hit the record high in Heathrow yesterday afternoon - breaking the previous record of 36.5C (98F) set on July 19 2006 in Wisley, Surrey.
Jonny Bradbrook, of Ravensworth Nurseries, Richmond, North Yorkshire, said his business was a scene of devastation after huge hailstones smashed thousands of planes of glass in his greenhouses.
Mr Bradbrook said the storm arrived at around 9pm yesterday and only lasted for 20 minutes, but left thousands of pounds of damage.
He said: "I've never known anything like it. They were as big as golf balls. I think there might be 5,000 panes gone but I'll know for sure later."
Mr Bradbrook said many of the panes were left with "bullet holes" and the broken glass has also wrecked some of his stock.
He said: "We've had floods before but nothing like this. There was no rain, just hail and thunder."