The Highway Code has limited advice regarding driving in hot weather:
Keep your vehicle well ventilated to avoid drowsiness. Be aware that the road surface may become soft or if it rains after a dry spell it may become slippery. These conditions could affect your steering and braking. If you are dazzled by bright sunlight, slow down and if necessary, stop.
You can either open your windows or use your air conditioning. If you don’t use your air conditioning frequently its effectiveness tends to diminish. It can be used to help defog windows quickly.
If you are on a bike, you’ll need to pay particular attention to the type of clothing you wear because it’s possible to overheat in very slow traffic, but suffer from hypothermia when riding fast because of the wind chill, even on a hot day.
If you are driving with your window down, or you have a convertible, be aware that you can get sunburned, and that carries with it the risk of you developing melanomas and skin cancers. The infamous ‘taxi driver’s arm’ (also called ‘white van man tan’) means you could end up with your right arm brown and your left arm pasty white.
Pets and children in vehicles
If it’s anything more than 15 degrees Celsius and sunny you should not leave pets in the car at all. Dogs have no cooling mechanism other than panting; they can overheat and die in a matter of minutes in a hot car. It is not enough just to leave the window open a crack as the temperature can still reach over 50 degrees Celcius quickly.
Children can also suffer heat exhaustion quickly, so take them with you when you leave the car.
Slipperiness after rain
When it has been dry weather for a while a surface layer of grime and oil builds up on the road. When it rains, this becomes extremely slippery. After a period of rain, and with cars driving over it, it is washed away.
Tar can melt if it is really hot. This can make some patches of road slippery. It also means that you might experience tar splashes on your car. There are commercial cleaning products to remove tar from your paintwork.
Black leather and black steering wheels can become blisteringly hot in the sun. Be mindful of children sitting on them in shorts. You can purchase shades for the rear windows to keep the sun off children and pets while you are driving.
Driving while you are hot will cause you to become dehydrated more quickly. This is especially pertinent for motorcyclists. Make sure you take on fluids regularly because dehydration reduces your ability to think and react, and therefore increases the risk you’ll have an accident.