the public has been urged to avoid travel as record-breaking temperatures they are predicted to reach the capital next week.
A national emergency has been declared in England after the very first red warning was issued for severe heat weather.
Early next week, record temperatures of as high as 41°C could occur around London, and Met Office chief Penny Endersby warned of “absolutely unprecedented” conditions.
Cabinet Minister Kit Malthouse said transport services are experiencing “significant disruption” as he urged people not to travel.
Ministers held a Cobra emergency meeting on Saturday after experts warned lives could be at risk from scorching temperatures.
After chairing the meeting, Mr Malthouse told the BBC: “It is clear that the carriers are telling people on Monday and Tuesday that they should only travel when absolutely necessary.
“Service will be significantly affected. For example, the heat will have consequences for the track, causing trains to run slower. There may be fewer services. People should be wary of disturbance.
“If they don’t have to travel, now might be a time to work from home.”
Mr Malthouse said steps have been taken to ensure hospitals and ambulances that may come under pressure were prepared, while schools were given guidelines to remain open.
He added in a separate statement: “It is important that we all continue to follow public health advice to keep cool and take simple precautions such as drinking plenty of water and seeking shade, as well as checking vulnerable friends and neighbors.”
The heat wave started on Saturday, with Heathrow Airport and Kew Gardens experiencing the highest temperatures of 29.1C.
The warm weather has increased demand for water in some areas, with South East Water confirming that residents of Challock and Molash, in Kent, had no water due to “sustained warm weather and significantly increased demand for water”, causing “our network came under considerable pressure”. .
A statement from the supplier read: “We continue to work on restoring your supplies and will continue to work on this tonight.
“As a precautionary measure, we will open the bottled water station at Challock’s village hall at 8am tomorrow morning.
“The team will be there until 7:00 pm tomorrow night.”
Meteorologists say there is an 80 percent chance that the mercury will surpass the previous record temperature of 38.7 degrees Celsius in 2019 in Cambridge next week.
Scorching temperatures are forecast on Monday, with Peterborough expected to reach 37C and Milton Keynes, Norwich and Lincoln expected to reach 36C.
Temperatures are expected to rise several more degrees on Tuesday – into the mid-30s for much of England and Wales.
There is a 50 per cent chance that temperatures will reach 40°C somewhere in the UK that day, likely along the A1 corridor which runs from London to Scotland through counties such as Lincolnshire, Nottinghamshire, Yorkshire and the North East.
After the Met Office’s first red warning of extreme heat, which covered a swath of England from London to Manchester and York Monday and Tuesday, CEO Penny Endersby said people may find it difficult to know what to expect when “climate change led to such unprecedented severe weather conditions.”
“Here in the UK we are used to treating a hot spell as an opportunity to go play in the sun,” she added.
“This is not such weather.”
The orange warning will initially apply to all of England on Sundays and will apply to southern Scotland and Wales Monday through Tuesday.
London Mayor Sadiq Khan held a special meeting on Friday with key senior officials from agencies including the NHS, the Met Police, the London Fire Brigade, the London Ambulance Service, City Councils and Transport for London to ensure a robust plan is to get the level four heat warning.
Khan has urged Londoners to only undertake essential journeys on Mondays and Tuesdays and to prepare for disruptions as speed limits will apply on train and tube networks.
The mayor also issued a high air pollution warning for London on Monday.