My phone went to a black screen in the cold weather.

i was at work shoveling snow and realized my phone turned off. i took it inside knowing that the phone shuts off in order to protect itself. once i finished what i was doing i checked on my phone and after a long while it had come back on. i used it (inside) for less than five minutes and boom it went black again and won't come back on. I've charged it, try to reset it, nothing. its unresponsive. i sent it to a repair guy to change the battery but still it doesn't turn on. please help me.

weather temps were around 30°ish

but the week before was colder the phone did the same as above but worked fine as soon as i took it inside.