Motorists are being urged to prepare for all eventualities during the extreme weather conditions amid warnings that thunderstorms and heavy downpours could follow this week's record high temperatures.  

National Highways has repeated its call for motorists to carry out vehicle checks before they set off and carry drinking water with them with soaring temperatures continuing across the country. 

The Met Office has advised that extreme heat can also bring variables of weather and says thunderstorms and showers could occur later in the day and overnight once temperatures have peaked. 

National Highways says sudden rainfall onto hot and dry roads can make conditions on the road slippery for drivers because oil and grease build up through the hot weather, so motorists are asked to take extra care.

When driving in heavy rain and waterlogged roads, motorists are urged to slow down and keep well back from the vehicle in front. They should also ease off the accelerator, slowing down gradually if the steering becomes unresponsive.  

Mel Clarke, Customer Service Director for Operations at National Highways, said: "We encourage drivers to check the latest weather and travel conditions before they travel as well as carry out important car checks such as looking at their oil, tyres and coolant levels. Amid the extreme heat warning we have also been advising motorists and their passengers to carry bottles of drinking water with them to keep hydrated. 

"With the possibility of thunderstorms and rain later on in some areas to factor in, it is important for everyone to allow more time for their journey and drive according to the weather conditions." 

National Highways has advice pages on its website around travelling in the summer, and will continue to provide social media and traffic updates during the coming days. 

Drivers considering travelling over the coming days should: 

• Take a bottle of water before setting out to ensure you stay hydrated 
• Plan and leave plenty of time for journeys 
• Check the weather forecast for your destination 
• Check your vehicle before you leave
• Check travel conditions before setting out and, where it is safe to do so, during journeys. 

Among its tips for driving in the summer, National Highways says during particularly hot weather, make sure your engine stays within the normal operating temperature range. However, if it begins to overheat, find somewhere safe to stop and allow it to cool down. 

Our motorways and major A roads are highly resilient to extremes of weather, including hot weather. The design and build standards we apply to our roads are considered best practice and are adopted by other countries around the world. 

Rain makes it harder for tyres to grip the road and harder for drivers to see ahead – significantly increasing the chances of being involved in a collision. 

In the event of a sudden downpour during this period of hot weather, drivers should: 

• Slow down if the rain and spray from vehicles is making it difficult to see and be seen and remember that stopping distances will be at least double in wet weather, because your tyres will have less grip on the road.
• Keep well back from the vehicle in front as this will increase your ability to see and plan ahead
• Ease off the accelerator and slow down gradually if the steering becomes unresponsive as it probably means that water is preventing the tyres from gripping the road.

National Highways is advising drivers to pay attention to messages on the overhead electronic signs, listen for radio updates, keep pace with social media updates or call the National Highways Information Line on 0300 123 5000.