For the first time in more than a month it’s actually chilly outside. A graph of yesterday’s hourly temperatures tells the story. The day started out warm but temperatures pretty much fell continuously until a couple of hours ago. The normal daytime heating was overwhelmed by the onrush of cold arctic air.

There was a 33 degree difference between yesterday’s high and low temperatures. That’s triple our normal daily temperature range in January, but it doesn’t match up to the largest range we found. Gothamist has daily temperature data back through 1971. January 9th, 1978 also saw the passage of an arctic front. That day started out at 58 degrees and ended at 15 for a range of 43 degrees. Double digits above and below normal in one day!

Gothamist: Winter’s Belated Beginning.