Explained | How to help your smartphone survive a heatwave

By Coco Liu

Just like humans, most smartphones function best within a certain temperature range. For devices made by Apple and Samsung, it’s 32°F-95°F (0°C-35°C), while China’s Xiaomi boasts an upper threshold of 104°F. As extreme heat becomes more common, more phones are spending time outside that comfort zone.

Once a phone exceeds its normal operating temperature, built-in thermal sensors trigger a series of actions that can include temperature warnings, slowed operations and even shutoff. That’s a feature designed to keep the phone intact while it cools off. But frequent exposure to heat distress can also reduce the lifespan of a smartphone’s battery and damage other internal components.

Industry-wide data is hard to come by, but Asurion — a US firm that provides phone insurance services and runs about 700 smartphone repair stores — observed nearly 15 per cent more battery-related issues during last year’s record hot summer compared to the rest of 2023. As this summer shapes up to be even hotter, here’s what you need to know about keeping your smartphone cool, calm and collected.

When do smartphones start to overheat?

Pretty much everything you do with your handset creates heat, and since smartphones can’t sweat like humans, that heat builds up. When temperatures outside are also high, it doesn’t take long for a phone’s temperature to rise significantly. During last year’s heat wave in Europe, for example, temperatures topping 45°C (115°F) killed a number of mobile phones on the Italian island of Sardinia.

“It’s only once you get to an ambient temperature of 110°F or higher, or when the device is exposed to direct sunlight on a very hot day, where the vast majority of phones will begin to run into issues,” says Tom Paton, founder of Green Smartphones, an online phone-comparison platform.

That kind of heat is becoming more common as global temperatures rise. May marked the Earth’s 12th consecutive month of record-breaking temperatures, and included heat waves in India, Thailand and Egypt. In the US, a heat dome building over the mid-Atlantic is expected to break temperature records this week.

How do you know if your phone is in distress?

Most smartphones warn users about imminent overheating. Third-party apps such as AIDA64 (for Android and iOS) and Cooling Master (Android) can also monitor real-time phone temperatures. Paton applies a more basic rule of thumb: If your phone gets uncomfortable to hold, it’s beginning to overheat.

A phone that’s performing slowly is another red flag, says Nicholas Bains, a smartphone expert at Asurion. The phone will deliberately slow down its processing so it doesn’t produce even more heat, though Bains warns that this can sometimes happen too late to prevent damage. “Your phone is able to protect itself in the moment,” he says. “But frequent and repeated exposure to high heat can have long-term effects on your phone’s performance and can permanently shorten its battery life.”

How can overheating damage your phone?

Heat presents a major risk for a smartphone’s battery. While the battery degrades naturally over time, prolonged exposure to high temperatures can wear it out prematurely, says Kyle Wiens, chief executive officer of iFixit, an electronics repair business and advocacy group. The adhesive used for phone screens can also start to loosen once temperatures exceed its melting point, Wiens says.

Paton adds that the phone’s central processing unit (CPU) can be damaged if its maximum operating temperature is exceeded. In extreme and rare cases, heat buildup can result in battery combustion, which can cause a fire or small explosion.

But most immediately, you’ll experience a loss of functionality and potentially data, as overheating causes apps to glitch or crash.

How can I protect my smartphone from heat?

Keep your phone out of direct sunlight, or anywhere else the heat might be magnified (like the dashboard of a car).

Avoid intensive phone use. The less a phone’s processor has to run, the easier it is for the device to stay cool. To minimize background activity, try using Airplane Mode.

Remove your phone case. If you don’t want to strip your handset, there are also phone cases designed to achieve better heat dissipation by using breathable materials and increased airflow.

Charge your phone in a cooler environment. Charging itself generates heat, so try to avoid it when your phone is already hot. If you must charge, don’t use the phone while it’s juicing up.

Let an overheated phone cool down gradually. Your smartphone doesn’t like heat, but it also doesn’t like extreme temperature fluctuations. Putting a phone in the refrigerator to cool it down, for example, can be as harmful as letting it overheat in the first place. “Sudden temperature changes can cause additional damage to internal components,” Paton says.