What the Record May Heat Means for Your Tyres and the Risk of a Summer Blowout

Britain has baked through one of its hottest ends to May on record, and the heat does more than test your patience in a queue of traffic. It puts real strain on the parts of your car that keep you safe and moving, and tyres sit right at the top of that list. As temperatures climbed towards the mid-thirties over the bank holiday weekend, breakdown patrols reported a sharp jump in call-outs, and tyre specialists issued warnings about a hidden risk that catches out even careful drivers: the air inside a hot tyre expands, and an over-inflated tyre is far more likely to blow out at speed. A two minute check before you set off can be the difference between a smooth journey and a frightening, expensive failure on the motorway.

The warning lands during a spell of exceptional heat, with reports of temperatures reaching 35.1C at Kew Gardens in west London. The AA said it attended 34,124 breakdowns between the Friday and Monday of a recent bank holiday weekend, a 15% increase on the same period in 2025, with the largest jumps on the Sunday and Monday at around 21% year on year. Heat, long journeys and cars that have sat unused for months are a difficult combination, and tyres, batteries and cooling systems take most of the punishment.

Why heat turns a healthy tyre into a hazard

The science is simple but easy to overlook. Air expands as it warms, so the pressure inside a sealed tyre climbs as the temperature rises. On a hot day, the road surface itself can be far hotter than the air, and the constant flexing of the tyre as it rolls and corners generates yet more heat. Stack those effects together and a tyre that was correctly inflated on a cool morning can become noticeably over-inflated by the afternoon. An over-inflated tyre has a smaller contact patch with the road, which reduces grip and braking performance, and it is under more stress, which raises the chance of a sudden failure.

A blowout is one of the most dangerous things that can happen to a moving car. The sudden loss of pressure can wrench the steering, make the vehicle difficult to control and, at motorway speed, put the driver and everyone around them at risk. Even when it does not cause a crash, a blowout can wreck the wheel and damage surrounding components, leading to repair bills running into the hundreds of pounds. The frustrating part is that many blowouts begin with a problem that was visible or measurable beforehand, such as low tread, a bulge in the sidewall, a slow puncture or pressure that has crept too high in the heat.

A spokesperson for tyre specialist Yellowhite explained the most common mistake drivers make. “Your tyres warm up when you drive, and you can get a false pressure reading when they’re warm,” they said. “Check your tyres before you set off, when they’re cold, for an accurate reading. It’s important to check your tyre pressure regularly anyway, but during the extreme heat like we’re expecting this weekend, it becomes absolutely critical.” Checking a hot tyre and then letting air out to hit the recommended number can leave it dangerously under-inflated once it cools, so timing the check really does matter.

The legal and financial stakes

Tyres are not just a safety issue, they are a legal one. The minimum legal tread depth in the UK is 1.6mm across the central three quarters of the tyre and around its entire circumference. Drive on a tyre below that limit and you risk a fine of up to £2,500 and three penalty points per tyre, so a car with all four illegal could in theory cost you your licence and a five figure sum. Bald or damaged tyres will also fail an MOT, and they perform especially poorly in the heat when the rubber is already working hard. Tyre condition is one of the areas under scrutiny as part of the wider shake-up of driving laws aimed at cutting road casualties.

There is an insurance angle too. If a blowout or crash is later linked to tyres that were illegal or obviously defective, an insurer may reduce or dispute a claim, leaving you out of pocket. Keeping tyres legal and correctly inflated is therefore not only safer, it protects the cover you have paid for. With premiums beginning to climb again across the market, the last thing any driver needs is a preventable claim being challenged over the state of their tyres.

Correct pressures also save fuel. Under-inflated tyres increase rolling resistance, which makes the engine work harder and burns more fuel, while the wrong pressures wear tyres unevenly and shorten their life. At a time when pump prices remain stubbornly high, keeping every tyre at its proper pressure is a small habit that quietly pays for itself across the summer.

It is not only the tyres

Heat tests the whole car. The cooling system works hardest in high temperatures, and low or old coolant can let an engine overheat, which in the worst cases causes serious and costly damage. Before a long trip, check the coolant level when the engine is cold and top it up with the correct type if needed, and watch the temperature gauge on the move. If it climbs into the red, pull over safely and let the engine cool rather than pressing on.

Car batteries also suffer in the heat, despite the common belief that only winter kills them. High temperatures can cause the fluid inside a battery to evaporate and shorten its life, and a battery weakened over the summer often fails on the first cold morning of autumn. If your battery is more than a few years old or the car has been standing for a while, it is worth having it tested. A large share of the AA’s bank holiday call-outs involved batteries and tyres, the two components most easily checked at home before a journey.

Air conditioning deserves a mention because it is a safety feature, not a luxury, in extreme heat. A driver who is too hot becomes tired and less alert, so working air conditioning helps you concentrate. If yours is blowing warm, it may simply need a regas, and getting that sorted before a long drive makes the journey safer as well as more comfortable. Carrying water for everyone in the car, including pets, is sensible on hot days, especially if you could be caught in a jam.

What to do

Check your tyre pressures when the tyres are cold, meaning the car has been parked for a few hours or driven no more than a couple of miles. Use the manufacturer’s recommended figures, which you will find in the handbook or on a sticker inside the driver’s door frame or the fuel filler flap, and remember that many cars list a higher pressure for a fully loaded vehicle, which is useful for a holiday run. Do not simply let air out of a warm tyre to reach the recommended number.

While you are there, run a quick visual inspection. Look for cuts, bulges or objects stuck in the tread, and check the depth using the 20p test: insert a 20p coin into the main grooves, and if you can see the outer band of the coin, the tread may be below the legal limit and the tyre should be checked by a professional. Do not forget the spare, if your car has one, and the tyre repair kit if it does not. Inspect tyres before any long journey during the hot spell, after long motorway trips, and at least once a week through the summer.

Finally, plan hot weather journeys with a little care. Travel earlier or later in the day to avoid the worst of the heat, keep the fuel tank topped up in case of delays, and make sure your breakdown cover is current before you set out. None of these steps takes long, but together they dramatically cut the odds of joining the tens of thousands of drivers who found their weekend interrupted at the roadside. In a heatwave, the few minutes you spend in the driveway are some of the most valuable of the whole trip.

Sources:

• NationalWorld: Urgent heatwave tyre warning for drivers as temperatures soar
• GOV.UK: Tyre safety and the law