Personally I don't fly below 0C as per DJI's recommendation. DJI's battery management systems do adjust for the cold, but only within their recommended flying temperature range. Some people get away with it but I have read too many stories of cold weather battery failures, gimbal issues, and iced props. Everyone has a different threshold for what they are comfortable with though, and it's a calculated risk. Everything works fine...until it doesn't
If you're going to do it, keep the batteries very warm until you're ready to fly, as well as your controller and smartphone/tablet.
The other problem is with the smartphone or other device used to fly - they fare much worse in the extreme cold than the DJI controller and it's not uncommon for them to suddenly drop to 0% or have touch screen issues (my iPhones would always become essentially useless in the extreme cold). DJI seems to have solved this with their new
smart controller with a rating down to -20C, probably because it generates so much of its own heat.
There is also the issue of condensation, which will be most noticeable on the camera lens but will affect the whole drone any time you move between extreme temperature changes. If you can't avoid this, you can use a plastic bag to minimize the condensation, and keep it in a case for as long as possible to make the temperature changes as gradual as possible.
The Inspire drones warn you when the battery temperature is below 15C and has a heating function. Some people build heating pads into their hard cases as well to keep the drone & accessories toasty warm before flight. You can buy battery warmers as well but most of them use the battery's own power to warm them.