What you should not do:
Experts have for years pointed out that’s a bad idea – and now Apple is officially warning users not to do it.
“Don’t put your iPhone in a bag of rice. Doing so could allow small particles of rice to damage your iPhone,” the company says in a recent support note spotted by Macworld. Along with the risk of damage, testing has suggested uncooked rice is not particularly effective at drying the device.
What you should do:
If your phone isn’t functioning at all, turn it off right away and don’t press any buttons. The next steps depend on your specific circumstances, but broadly speaking: dry it with a towel and put it in an airtight container packed with silica packets if you have them. Don’t charge it until you’re sure it’s dry.
The heat does help defrost/defog quicker. Hot air can hold more moisture than cold air plus it needs thermal energy to transition from solid/liquid to gas.
For a phone, the heat is mostly bad because the phone itself is generating heat that it needs to dissipate, so blasting it with hot air will reduce its cooling efficiency and it will find a new equilibrium at a higher temperature. But if the phone is off, I wouldn’t be surprised if it’s fine in the heat (but I also wouldn’t be surprised if it causes issues with some adhesives, so maybe don’t blast it on max unless you can comfortably keep your hand close to the vent).