The summer solstice, 21 June 2017 was also the hottest day for more than 40 years, in fact since 1976. At London Heathrow the temperature reached 34.5 C.
From BBC :
Hottest June day since summer of 1976 in heatwave
21 June : The UK is basking in its hottest June day in 41 years, with a temperature of 34.5C (94F) recorded at Heathrow.
The Met Office reading at the London airport is the highest in June since the mercury hit 35.6 (96F) in 1976 - the all-time high since records began.
The heatwave has seen five sizzling days in a row during which temperatures in parts of the UK have topped 30C.
But weather warnings have also been issued for rain, with thunderstorms expected in some areas.
BBC weather presenter Chris Fawkes said: "To have these really prolonged spells, you need a block of high pressure that directs other weather fronts away.
Then we get the hot weather coming up from Europe."
Storms are forecast for some areas later in the day, and yellow weather warnings for rain in parts of England, Wales and Scotland are in place until the early hours of Thursday.
Our presenter added: "It is all going to go bang tonight.
"The hot air from the surface will meet with colder air coming in from the Atlantic and we will have some big thunderstorms, gusty winds, heavy rain and, in some places, even hail.
And as I type this on 22nd morning, the clouds are gathering and thunder is in the distance. However we do need the rain.
It is also the last week of Ramadan. In London on 21st the fasting times were 02.40 - 21.25. That is a long day. However these times don't coincide with sunrise and sunset, as these are 04.43 and 21.20, which is 16 hr 38 min of daylight [time&date] . So I wonder if the fasting times in the UK are adapted to start and finish early.
In the Arctic Circle countries the sun never sets at this time of year. Interesting article on Muslims in northern Finland where fasting lasts 23 hours and 5 mins, as the sun only sets for 55 mins - see The Independent. Some Muslims chose to stick to these times, others follow a Middle East timetable.
Incidentally Ramadan 2016 was the longest days of fasting in 33 years, see BBC.
See my 2016 blog with info on the summer solstice.