I have flown several commercial jobs in -20f. Place your bird on the ground for a couple of minutes to acclimate the temp. Keep your bats warm until your your ready to start the motors. After starting raise up and hover about a foot or two above the ground for a minute or two to warm it up. I have flown a couple of bats at over 20 minutes this way.
If there is any moisture in the air you can wipe a little anti-freeze on the blades to keep them from icing up. Otherwise, you need to check them frequently so you don't lose the bird because of Ice.
When you land, I use a garbage bag to put the bird in, close it up tight to remove as much air as possible and seal it. Then let it return to normal temps in the bag. Otherwise If you just bring it into the warm vehicle as mentioned above it will collect condensation from the air in the vehicle.
You can also check the groups and youtube for others with cold weather flying.
Good luck and Fly Safe!