As the UK experiences its third heatwave of the year, with temperatures set to reach 35°C in isolated locations on Friday and Saturday, experts have issued a stark warning to iPhone owners: charging your device incorrectly in hot weather could permanently damage the battery.
Apple's Official Warning
Apple explicitly warns that charging an iPhone in rooms above 35°C can permanently reduce battery lifespan. Similarly, Google advises that if a Pixel phone becomes too hot to touch, users should avoid handling it. The Met Office has reported increasing humidity towards the end of this week, exacerbating the risk for devices left in warm environments.
Worst Places to Charge Your Phone During a Heatwave
Ed Stapleton, tech expert at Clicks Geek, revealed the worst places to charge a phone during a heatwave, including under pillows, on windowsills, and in cars. He explained: “The mistake people make is thinking the charger is the only thing heating the phone up. In reality, the room, the surface, the case, the apps running in the background and direct sunlight can all add to the temperature.”
“Charging a phone on a sunny windowsill, a garden table, a car dashboard or under bedding is a bad idea during a heatwave. The battery is already generating heat while charging, and when you add direct sun or trapped heat on top of that, you are putting the device under much more stress than usual.”
Hidden Battery Damage
Stapleton emphasised that battery damage is not always immediate or obvious. “Your phone might seem fine after cooling down, but repeated overheating can reduce how long it lasts on a full charge over time,” he said. A phone left on a windowsill for an hour can quickly become hot to the touch, especially if running video calls, social media, or the camera, which further increases temperature.
Cars present a major issue as well. Using sat-nav, mobile data, and charging all generate heat. Leaving a phone on the dashboard in direct sunlight subjects it to far more pressure than indoor use. Stapleton advised: “If you are using your phone as a sat-nav, avoid leaving it directly against the windscreen for long periods in hot weather. Try to keep it shaded where possible, take the case off if it starts getting hot, and avoid charging it continuously if the device is already warm. People often plug the phone in because maps drain the battery, but if the device is baking in the sun at the same time, you are solving one problem by creating another.”
Bedtime Charging Risks
Charging phones on beds, sofas, or under pillows overnight is another common mistake. Fabric traps heat around the device and charger, making it harder for the phone to cool itself. This is especially problematic during a heatwave when bedrooms may already be hot late into the evening.
Safe Charging Practices
Stapleton recommends charging phones on a cool, hard surface away from sunlight. “A bedside table, desk or kitchen counter away from direct sun is much better than a windowsill, bed or sofa. Hard surfaces help heat escape more easily, while soft furnishings and thick cases can keep heat trapped around the device,” he explained. If your phone feels hot, unplug it, remove the case, and move it somewhere cooler. Do not put it in the fridge or freezer, as sudden temperature changes can cause condensation. Allow it to cool naturally in the shade.
