It can be cold (like it's been here for the past week, along with a foot or more of snow in my area) but the wind chill is the most important factor in cold weather.  WInd chill is what makes the wind feel as cold as it REALLY is.  Not what the thermometer shows but what the WIND tells the thermometer to show.  You hafta go to a professional website (like NOAA) in order to get a true read on temperatures and the temp fluctuations.

Just do it, it's really kinda fun to track this stuff.