The opening day of County Championship games between Gloucestershire and Hampshire, and Northants and Lancashire on Tuesday have been shortened due to the red extreme heat warning.
Play will finish at 16:30 BST instead of 18:00 in the “interest of spectator and player welfare”.
They will still start play at 11:00, with time to be made up from Wednesday.
The UK could have its hottest day on record this week, with temperatures forecast to hit up to 41C (106F).
The Met Office has issued a red extreme heat warning on Monday and Tuesday in much of England, from London and the south east up to York and Manchester.
Gloucestershire, whose game with Hampshire forms part of the 150th anniversary edition of the Cheltenham Cricket Festival, said the decision to alter the playing hours on Tuesday had been taken “in line with advice” from the England and Wales Cricket Board.
A statement added: “The decision has been taken in unison by both Gloucestershire and Hampshire in the interest of spectator and player welfare, to allow everyone in attendance to avoid the extreme heat that is expected towards the end of the day.”
Northants say those with a general admission ticket for Tuesday can also use their ticket for entry on day two of the match.
Meanwhile, England have brought forward training by an hour, to 10:30, on Monday and Tuesday as they prepare for their Women’s Euro 2022 quarter-final against Spain on Wednesday.
And in horse racing, five meetings across Monday and Tuesday have been cancelled because of the extreme heat.
Monday’s meets at Beverley and Windsor have been cancelled, as have Tuesday’s fixtures at Chelmsford City, Southwell and Wolverhampton.