She said there is a snowstorm outside. I went to the front where the windows were - WOW! There was already a half a foot of snow and it was just the beginning. It was a beautiful sunny day when we entered the hall. There was no sign of this storm before hand. So your remark about Chicago weather can change in 15 minutes, I can attest to!
Yep, mix some warm air from the Gulf, some cold air from Canada, and plop a big old lake right where they meet, and you never know what is going to happen.