Motorists attempting to cool down during the heatwave in stationary vehicles with the air conditioning running risk fines under emissions laws, with the RAC warning that engine idling causes air pollution.
Standard penalties are £40 if issued by a police officer, or £80 from a civil enforcement officer, both halved if paid promptly. Some local authorities, however, impose larger fines.
In London, Islington Council enforcement officers issue £110 fines to those who refuse to switch off an idling engine after being asked.
RAC senior policy officer Rod Dennis said: “Air conditioning is a gamechanger in modern vehicles, making otherwise uncomfortable journeys by road a genuinely pleasant experience.
“We even advise those driving vehicles without air-con to consider delaying any non-essential trips this week until the heatwave passes.
“But while we’re all desperate to stay cool, just sitting in the car with the engine and air-conditioning running and going nowhere isn’t advisable.
“Due to the air pollution this causes, you risk a fine from a police or civil enforcement officer.”
In 2019, the Conservative government announced plans to introduce higher fines for drivers who idle, but this never took place.
Lord Chris Grayling, then-transport secretary, said at the time that combating idling would be “an easy way to drive down dangerously high levels of pollution”.
Temperatures could hit 40C on Wednesday and Thursday in some parts of England and Wales as a “heat-dome” settling over western Europe has brought extreme conditions across the continent.
People have been warned to stay out of the sun between 11am and 3pm as the severe heat is expected to cause a danger to life.
During the peak of the heatwave on these two days, the temperature could come close to the UK’s all-time high of 40.3C, which was measured in Lincolnshire in July 2022.
The latest heatwave is also expected to surpass the record for June of 35.6C set in Hampshire in 1976.
A combination of extreme heat and humidity could have an impact on public health, infrastructure, power and water supplies, the Met Office said, and could cause heat-related issues for a range of sectors such as transport, energy and water supply.
There could also be an increase in water safety incidents during the heatwave, the agency said, as more people are likely to visit coastal areas, lakes or rivers.
The Met Office has issued another amber warning for heat for Friday, covering eastern and central England, as the exceptionally hot weather looks set to linger late into the week.
The forecaster also said it may need to issue further updates on the extreme weather as more details on the conditions become clear.
Grahame Madge, Met Office spokesman, said: “We have issued another amber warning for eastern and central England for Friday.
“As the forecast continues to evolve we may need to issue further updates once more detail becomes clear.”
