When you log into Facebook and notice that all of your local friends have pretty much the same comment....
"Woke up to frost on the grass!"
"Had to scrape the windshield this morning!"
"Needed to scrape my windshield and couldn't find the scraper. Had to use a credit card instead"
"Had to dig out the gloves this morning. Hats and scarves will be next."
I don't know what would give it away that it was chilly here this morning? Do you?