Expected high temperatures have prompted Londoners to be urged against travelling on Monday and Tuesday.
The current heatwave is set to peak on Tuesday, with an 80 percent chance of the mercury topping the UK’s record temperature of 38.7C (101.7F) set in Cambridge in 2019.
Transport for London (TfL) is advising passengers to only travel for “essential journeys.”
The firm’s chief operating officer Andy Lord said: “Due to the exceptionally hot weather that is expected next week, customers should only use London’s transport network for essential journeys.
“If customers do need to travel, they should check before they travel as we are expecting there to be some impact to Tube and rail services as a result of temporary speed restrictions we will need to introduce to keep everyone safe,” he added.
“It is also vital that customers always carry water at all times with them when travelling.”
The Met Office has issued an amber warning for heat covering much of England and Wales from Sunday until Tuesday.
There is a 50 percent chance of temperatures reaching 40C somewhere in the UK, likely along the A1 corridor, with the Met Office also issuing its first red warning for extreme heat.
Very hot temperatures can affect rails, overhead power lines, and signalling equipment, with TfL saying it will work hard to keep as many services running as possible using “enhanced” inspections to mitigate the impact of the heat.
Track temperature checks will continue to be carried out regularly across the Tube and rail networks to ensure they remain safe and that the track is not at risk of bending or buckling, TfL said in a statement.
It added it was also inspecting the air conditioning units on the trains that cover 40 percent of the Tube network, the trains on the Elizabeth Line and London Overground as well as the air cooling units on double-deck buses to ensure they are functioning well.
TfL also has response teams standing by on its rail and road network to deal with any issues as they occur, with a particular focus on stalled trains and times, crowding and customer advice.