My phone shut down twice last August while it was running navigation. Both times it was on the dashboard, both times it was ninety five degrees outside, and both times I lost my route in the middle of an unfamiliar city.

Phones shut down on purpose when they get hot. It is a protective feature, not a malfunction. But you can stop it from getting there.

The dashboard is the worst place in the car

Sitting on the dash means direct sun through the windshield plus heat radiating up from the dashboard itself. On a hot day that surface can hit 150 degrees. Your phone is in the hottest place it could possibly be, mounted where you can see it.

Move the mount to an air vent. Air conditioning blowing on the back of the phone is the single most effective cooling you can get in a car. Even the passenger side vent helps.

What to do while navigating

1. Take the case off on hot days. A thick case traps heat. This makes a bigger difference than people expect.
2. Turn the screen brightness down. The screen is one of the two biggest heat sources in the phone, and in daylight we all crank it to maximum.
3. Charge it only when you have to. Charging generates heat on top of everything else. If the phone is already hot and fully charged, unplug it.
4. Aim one vent at the phone, even at a low fan speed. Constant moving air beats an occasional blast.

Do not put it in the freezer or the cooler. Rapid cooling causes condensation inside the phone, and water damage from condensation is not covered by most warranties. This is the one home remedy that causes real damage.

Signs you are already too hot

• The screen dims on its own and you did not touch the brightness setting.
• The camera app refuses to open or the flash is disabled.
• Charging slows to a crawl or stops.
• The phone feels hot through the case, not just warm.

If any of those happen, close the navigation app, take the case off, and let it sit in front of the vent. It usually recovers in a few minutes.

The long term fix for me was switching to a vent mount and using a sunshade on the windshield when parked. The phone has not shut down once this summer, including a week where the dashboard read 102 degrees.