Apple Watch overheated under the sun and temperature warning showed up. They have cooled down for the whole night and still didn’t turn on. It doesn’t response any button, hard reset either. After trying to charge them temperature sign shows up, however they are not heated.
Apple Watch
If the temperature alarm is still showing on your Apple Watch when it is obviously cool (doesn’t feel hot to touch) it is likely the sensor has failed and is giving a false indication. You have tried the reset without success, so it is not stuck software. Your next step (the only remaining step) is Contact Support (link) and arrange to get the watch examined and serviced by Apple.
Apple Watch overheating under the sun and not turning on
