Schools in central London are adopting continental opening hours in an attempt to beat the heatwave.
Most schools will close at 1330 BST - two hours early - over the next few days while others have called off their sports day, Westminster Council said.
The move is part of a number of measures being taken to prevent people falling ill as temperatures soar.
Advice on how to keep cool and hydrated will also be given to elderly people and the homeless.
Soho Parish Primary School and Our Lady of Dolors are among those that have suspended their sports day.
The council said parents had been informed if opening hours have changed but urged anyone who was in doubt to check with their school.
Schools in Westminster are due to finish for the summer holiday on Friday.
Council workers will also be visiting elderly people in their own homes and care homes to offer tips on how to stay cool.
They will be going out on the streets to give advice to homeless people on coping in the heat.
Cllr Ian Adams, said: "Heatwaves like the one we are experiencing now can cause a lot of unnecessary illness, especially among old people, who are particularly vulnerable.
"Our advice is simple - stay out of the sun where possible, dress in light clothes and stay hydrated."