The ECB have altered the County Championship's playing conditions for the opening day of this week's fixtures in anticipation of the hottest day on record in the UK, with forecast temperatures of up to 41C (106F).
Gloucestershire and Northamptonshire both confirmed on Monday that they would make use of the changes and cut the length of each session by half an hour in order to avoid the extreme temperatures expected on Tuesday evening.
Other counties will consider making use of the ECB's provisions, which will see the scheduled close of play brought forward to 4.30pm local time, but both teams must agree to the optional change.
"The hours of play on Tuesday may be shortened to 3 x 90-minute sessions, a reduction of 30 minutes in each session," the ECB told the counties. "Lunch and tea intervals will be of the usual length meaning that the scheduled close of play would be 1630, thus avoiding the heat that is predicted at the end of the day.
"The time not played on Tuesday as a consequence will be caught up by adding 30 minutes to each of Days 2, 3 and 4 with sessions of 2¼, 2¼, 2 hours. Please note that the playing conditions regarding making up of time/time carried forward are not altered and will be applied as normal."
Gloucestershire said they had made the decision "in unison" with their opponents 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 said in a statement that tickets for the first day of their fixture against Lancashire would also be valid for the second, and reminded fans "of the importance of staying hydrated and taking appropriate action to protect themselves from the sun".
Middlesex confirmed they would not shift the timings of their game against Sussex, though the MCC have loosened the pavilion dress code by removing the stipulation that members must wear a jacket - though they still need to wear ties and formal trousers.
"The players are happy to just get on with normal playing hours," Richard Johnson, Middlesex's coach, said. "Most of them have been abroad and played in this sort of weather before so are happy to just keep it regulation."
Mickey Arthur, Derbyshire's coach, said: "There's an England Lions tour to Sri Lanka next year. If you think this is hot, wait until you see what Sri Lanka's going to dish up for you. Our boys have to be able to handle the conditions. Hopefully we'll win the toss and bat, but you never know."
The women's ODI between England and South Africa on Monday included additional drinks breaks, while the ECB are not anticipating any changes to the playing conditions for Tuesday's men's ODI between the same teams.