It is impossible to take photos with my iPhone 6 in winter. Temperature can be from 0 Celsius (32 Fahrenheit) to minus 10 Celsius (14 Fahrenheit) i.e. not very low. Phone just turns off without any explanation. I can warm it inside my pocket or coat and take out only for few photos -- it doesn't help.
Once in room it recovers.
Other phones and cameras work well in such conditions.
How to solve this? I suspect they just put some explicit trigger inside.