Was getting chilly - about 35 F out. I previously have only had trouble with idevices when they get too hot.
Too hot is the processors cooking.
Too cold is the battery.
35F = 2 Celcius. Add wind chills and I this will cause your phone to drop voltage quickly.
Here's Why Your iPhone Battery Dies in Cold Weather - Orchard
And regarding your phantom 3, make sure you have that firmware that reduces prop propulsion when battery voltage drops too low from cold climates. There was a reported flock of phantoms dropping from the skies from cold weather, especially in the higher altitudes.