Did you know that minus 40 degrees is the same regardless of the scale used? Yep, 40 below is 40 below in both Celsius and Fahrenheit. Also, mercury freezes at minus 38 degrees Celsius. So if it gets really cold, your old-fashioned mercury thermometer will stop at minus 38 degrees.
Just because the sun is out on a winter day does not mean it is warm. In northern climates, the coldest days are usually the clear ones – no clouds to hold in what little heat may be radiating away from the earth. A wind chill rating of minus 25 degrees Fahrenheit or lower can cause skin to freeze (frostbite). If it is that cold out, make sure all exposed skin is covered – except your eyes, of course.