I have a table of Wind Chills (or straight temp if there is no wind) defining cold threats as follows:
400F to 210F COLD. Unpleasant.
200F to 10F VERY COLD. Very Unpleasant.
00F to -190F BITTER COLD. Frostbite possible. Exposed skin can freeze within 5 minutes.
-200F to -690FEXTREMELY COLD. Frostbite likely. Exposed skin can freeze within 1 minute. Outdoor activity becomes dangerous.
-700F and below FRIGIDLY COLD. Exposed skin can freeze in 30 seconds.