Spring officially begins Friday at 6:44 CDT, but today we're getting a little hint of it. Right now it's 19°C in Chicago; if it can squeak up to 22°C it will be the warmest day since October 12th.
Another trivial tidbit: because the earth's atmosphere bends the sun's rays a little, today, and not the official equinox Friday, is the day when we have 12 hours of daylight. From tomorrow until September 25th, days are longer than nights just about everywhere between the Tropic of Cancer and the Arctic Circle.
Update, 14:05 CDT: Yep, we just hit 22°C, warmest temperature in Chicago for 156 days. Why am I inside?