This also means that people in the area experienced a tropical night, as temperatures remained above 20C.
Charterhall in the Scottish Borders had reached 28.6C by mid-afternoon on Wednesday, making it the warmest September day in the country since 1906, when Gordon Castle in Moray reached 32.2C.
The high temperatures came as the UK was braced for storms, with heavy showers expected on Wednesday afternoon and a yellow weather warning issued in most areas on Thursday.
On Wednesday morning, a primary school in Plymouth, Devon, had to be evacuated after being struck by lightning, while flash flooding occurred in the seaside town of Salcombe
A spokesman for the Met Office told the PA news agency that further rainfall was expected in the South West on Wednesday afternoon.
“There is a weather warning for the South West today through the course of the afternoon and finishing at 9pm this evening,” he said.
“Looking at the radar now, there is a bit of a lull in most parts. It looks as if some of the heaviest bits have passed away but there is an ongoing risk of impact from further showers.
“There are a few showers coming up across parts of Hampshire, Dorset and Wiltshire but the worst of the impact is expected to be further west, such as Devon, Somerset and parts of Wales.
“The risk in those areas should ease overnight.”
The South East, as well as northern parts of England and Wales, could also see heavy rain but weather warnings are not expected to be issued in those areas.
On Thursday, a yellow weather warning for thunderstorms affecting most of the UK apart from the South East has been issued.
The Met Office has advised that there is a “small chance” homes and businesses could flood quickly, with damage to some buildings from floodwater, lightning strikes, hail or winds.
This may cause delays and cancellations to some train and bus services, while there may also be difficult driving conditions and road closures.
There is also a small chance that some rural communities could become temporarily cut off by flooded roads.
“Almost everywhere could see some storms on Thursday,” the Met Office spokesman added.
On Wednesday, a yellow weather warning was in place for the South West.
Devon and Somerset Fire and Rescue Service was called to Mount Street Primary School in Plymouth at 9.57am after the building was struck by lightning.
Pupils were left with wet clothing after being evacuated from the school in heavy rain. No-one was injured in the incident.
Thunderstorms also caused flash flooding in the seaside town of Salcombe, where police said dozens of businesses had been affected.
Pc Emma Buley, of Devon and Cornwall Police, tweeted a video showing flooding on Fore Street in Salcombe.
“Flash floods in Salcombe this morning has affected dozens of businesses. Please be careful driving if you get caught in the rain today,” she tweeted.