An amber weather warning for extreme heat has been issued across a large part of the UK ahead of further soaring temperatures this week.
The rare warning was first issued last July. It states that 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, which issued the warning, said it is in place from 12.01am on Sunday to 11.59pm, when temperatures are predicted to soar into the 30s.
The forecaster added that it could be extended to Monday next week.
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.
A statement from the Met Office said: “Population-wide adverse health effects are likely to be experienced, not limited to those most vulnerable to extreme heat, leading to potential serious illness or danger to life.
“Government advice is that 999 services should be used in emergencies only; seek advice from 111 if you need non-emergency health advice.
“Substantial changes in working practices and daily routines (are) likely to be required.
“Significantly more people are likely to visit coastal areas, lakes and rivers, leading to increased risk of water safety incidents.
“Delays on roads and road closures are possible, along with delays and cancellations to rail and air travel, with potential for significant welfare issues for those who experience even moderate delays.”
The extreme heat weather warning system ranges from yellow to red and indicates how likely and how much of an impact the weather will have on public life.
An amber warning states that temperatures are likely to have a high impact.
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.
It adds that this helps because slower trains exert less force on the track and reduce the likelihood of buckling, avoiding the major disruption caused by a buckled rail.
Tracks at Battersea Bridge, in south west London, were meanwhile forced to close on Monday after a fire broke out.
A Network Rail spokesperson said: “We were called to a fire on a bridge in Battersea around 0430 this morning, where a wooden beam was alight. We closed the lines on the bridge while the fire was being tackled by our friends at London Fire Brigade, and it was put out by 0600.
“We were able to reopen two of the three tracks on the bridge by around 0630 and all three were open by 0845, following a thorough inspection of the bridge. We’ll need to do some repair work, notably to a walkway that was damaged in the blaze, and we’re working on a plan for doing that as we speak.
“The cause of the fire is under investigation.”
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 on any journeys.
RAC Breakdown spokesman Rod Dennis said: “An amber warning for extreme heat over such a wide area is rare and as a result we strongly urge drivers in England and Wales to think carefully before they drive, and do everything they can to avoid a breakdown.
“This starts with checking the coolant and oil levels under the bonnet when the engine is cold. Oil should be topped up if it’s low, and if coolant isn’t between the ‘min’ and ‘max’ levels then drivers should top it up – or take it to a reputable garage to get it checked without delay.”
Hampshire County Council also said it was preparing to deploy gritters to protect cars against melting roads.
It comes as hot weather is predicted to continue on Tuesday and over the weekend.
The Met Office has said 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, ahead of a warmer weekend.
Temperatures are then 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 ahead, with rain forecast for Tuesday and Friday.
Clouds with sunny spells could be widespread across the two areas for the rest of the week, with temperatures remaining in the mid to high teens throughout the week.
— Met Office (@metoffice) July 11, 2022
They will also benefit from the scorching weekend temperatures ahead alongside some cloud, with highs of 22C predicted in Glasgow and Belfast.
Weather forecasting models suggest it is possible – though not likely – temperatures could reach 40C in the UK next weekend, which would break the current British temperature record of 38.7C set in Cambridge in July 2019.
However, a spokeswoman for the Met Office said it takes computer modelling into consideration when making its predictions and it believes the warmest weather will not reach 40C.
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.