crazy chicago weather

now, what could that be. you wake up, look out of the window and decide to put on your cute red spring coat, it's plus 11 Celsius out there and no trace of snow that had just fallen yesterday night. you go to school, walk out in the evening and it blows your head off, and you find yourself in the middle of a snow blizzard, oh, and sure enough it's not plus 11 any longer. where on earth is that possible but chicago???