Forecasters say there is a 30 per cent chance that Sunday will be the hottest day ever recorded in the UK.
On Monday, the Met Office issued an amber weather warning for extreme heat across parts of the UK ahead of further soaring temperatures this week.
The rare warning states there could be a danger to life or potential serious illness as a result of the scorching temperatures.
Other issues could include road closures and delays or cancellations to rail and air travel.
The Met Office said the warning is in place from 12.01am on Sunday to 11.59pm, when temperatures are predicted to soar into the 30s.
It is being enforced across the East Midlands, east of England, London, South East, North East, North West, South West, Wales, West Midlands and Yorkshire and Humber.
The warmest day on record in the UK was the 38.7C scorcher recorded at Cambridge Botanic Garden in July 2019.
On Monday, Wales recorded its hottest day of the year so far as the mercury reached 28.7C in Cardiff’s Bute Park.
In England, the temperature peaked at 32C in Northolt, west London.
England’s hottest day so far this year remains the 32.7C recorded at Santon Downham, in Suffolk, on June 17.
Network Rail has warned speed restrictions are likely to be in place this week on some parts of the network most affected by the hot weather.
Fire services have urged people to have picnics instead of barbecues during the warm weather after a spate of grass fires.
The AA Driving School and RAC meanwhile said motorists should carry water with them, start their journeys earlier in the day, plan their routes and check their vehicles before setting off.
Hampshire County Council also said it was preparing to deploy gritters to protect cars against melting roads.
The Met Office says the mercury is predicted to rise to 30C in London, Chelmsford, in Essex, and Sudbury, in Suffolk, on Tuesday while the rest of England is expected to see temperatures soar to the late 20s.
The whole of England is largely expected to experience sunny days with some cloud over the next week to match the temperatures of mid to high 20s.
It will cool off a little on Friday, with the north-west and north-east of England predicted to have some rain with temperatures reaching highs of 19C.
Temperatures are expected to spike to 32C in Reading and London on Sunday and in excess of 35C in the southeast.
Scotland and Northern Ireland meanwhile are predicted to have a cloudier week, with rain forecast for Tuesday and Friday.
Weather forecasting models suggest it is possible – though not likely – temperatures could reach 40C in the UK next weekend.
A Level Three Heat Health Alert has also been issued by the Met Office and the UK Health Security Agency (UKHSA) from 9am on Monday to 9am on Friday in the east and south-east of England, with the rest of the nation having a level 2 alert in place.
The four-level system highlights the potential health impacts of these high temperatures.
On Monday, Met Office forecaster Simon Partridge told the PA news agency: “Parts of south-east England could exceed 35C on Sunday.
“At the moment, we are looking at a 30% chance of seeing the hottest temperature recorded in the UK.”