-7C so far today but its just the start of winter here so much lower to come, fingers were pretty cold and hurting a bit so got me some nice toasty gloves on order today, ones that you can use touch screens with.
I haven't owned either of my Mavics through the winter yet, but flew my Spark last year in -10F (wind chill -29F) and it flew perfectly.
After that I tried to just hover in -14F temps and see if the battery was considerably shortened and I concluded that there wasn't much of a difference.