Wat? No, -10 Celsius isn't cold enough for thermals. That's *almost* warm enough for shirt sleeves, especially if you're only going to be out for a few minutes. The ACTUAL scale goes like this:
-20F Awesome. Snow squeaks when you walk on it.
-10F Cold, wear gloves and a hat and stuff.
0F Snow crunches when you walk on it.
10F Chilly, definitely wear a coat.
20F Snow is kinda melty and packs easily.
30F Very melty, all snow turns to slush.
40F Refrigerator temperature.
50F Low end of room temperature range.
60F Perfect room temperature.
70F High end of room temperature range.
80F Break out the fans. Nursing home temperature.
90F Fans aren't really enough. AC helps more.
100F Body temperature. AC has trouble keeping up.
110F Medically dangerous, particularly if you run out of drinking water.