Dozens of schools have closed, many train services have been cancelled or delayed amid fears the searing heat could cause train tracks to buckle – and flights were suspended at Luton airport because of problems with the runway.
As the mercury soars to almost unprecedented levels – much of the country is under a red warning for extreme heat.
Wales has recorded its highest temperature ever, with 37C in Hawarden in Flintshire.
While in England, the hottest place was Santon Downham, Suffolk, which reached just over 38C this afternoon – making this the hottest day of the year so far.