You might have heard that joke during the recent cold snap - where record breaking lows were recorded over most of the United States (except west of the Rockies).
You probably didn't believe it, but it's actually true. Curiosity has been reporting temperatures between -24 and -13. Winnipeg, Minnesota, hit lows of -37.9. In fact, the highest temperature ever recorded on the surface of Mars? 95. I didn't believe it either.
So, yes, a few places were colder than Mars. Make you feel glad it's over?
The wide temperature swings are because Mars is a desert planet - if you've ever been to a hot desert, you'll know how rapidly the temperature can drop when the sun goes down. Moisture in the atmosphere evens out temperatures - and Mars has almost none.
Colder than Mars.