Thursday was the UK's hottest July day on record, with temperatures reaching 38.1C (100.6F) in Cambridge.
But was it the UK's hottest day ever?
While the Met Office says we can be sure it's the second hottest, it won't be able to confirm what is apparently its highest reading until next week.
Provisional figures released on Friday revealed a peak of 38.7C at Cambridge University Botanic Gardens. If verified, that squeaks past the UK all-time high of 38.5C, reached in 2003.
Why don't we know how hot it was?
Unlike the other weather station readings that report instantaneously, Cambridge University Botanic Gardens only reports at the end of the day - that's why it took the Met Office until Friday to release the provisional figure.
Alex Burkill, a meteorologist at the Met Office, explained any reading that challenges the all-time record should be carefully vetted.
He says each of the UK's weather observation stations is checked over every two years to make sure everything is still in good working order.
"Thermometers should be in shade and in ventilation," he said.
"The last time that the [Cambridge University Botanic Gardens] site had this check was the end of 2017.
"Because of the sensitivity of this reading, because it's the highest temperature ever recorded in the UK, we want to double check."
How can they be sure?
The Met Office has already sent out an engineer to inspect the station and its equipment. "They'll go out, check that the site looks fine, and that there's nothing untoward there," he said.
Anything from an overgrown tree to a new building nearby could alter the readings.
As well as checking the area, scientists will pore through all the readings from the day to check there wasn't a spike at the time of the hottest reading.
They would expect a gradual increase throughout the day, and any sudden change could indicate some temporary interference - like a car parked nearby.
So what are the chances?
Mr Burkill said the Met Office would be able to confirm the reading early next week but insisted he would be surprised if the reading did get discounted.
"Or another reading that hasn't come in yet might beat it," he said.