I took somebody's advice from a forum post I read and simply started the bird on the ground, and counted "alligator-1, alligator-2, ..." and let motors run before take-off for 1 minute. Twice this solved P3's complaining about cold battery, and it's pretty much a good idea anyways, being what we airplane pilors call a "run-up". It gives you a test to show that things are functioning well before you risk som altitude. I did a stick combo start and countes one minute, you could also auto-takeoff and hover for a while to warm up, run-up for more warmth.
Mind you, I didn't have batteries outside very long, this was a matter of taking the P3 from the warm house and flying just outside, parent's farm is a great place to get to. know the bird. If you were going "on location", where you might be outside for a while before flying, putting the battery inside your coat, or on the dashboard in the sun of a closed car (winter only), or in front of a heater vent for a while, might be good.
LiPo's would not want to be warm to the touch, but have their core temps above 40F/5C before flight. If they've been in the house, a few minutes exposure to cold should not matter much. If they've been outside all night in 10F/-12C I would warm them up by putting them on the kitchen table for 8 hours, not the oven.
Batteries don't need to be "warm", as much as they need to be "not cold", if you're going by touch.
As for wet, I did 2000 foot-long speed runs in nominal fog the other morning, no ill effects, no condensation. During the big snow melt a couple of weeks ago, I had a half-sheet of plywood that I put down as a launch pad, not bad as a dry spot and a maneuvering test for take-off/landing as I was getting to know the bird.
Long post I know, but hopefully addressing the subject at hand.