Winter is a dish best served cold
There are a lot of different ways people have to determine when it becomes winter. For clarification here, I'm only assuming the existance of 2 seasons: winter and summer. Yes, there are actually 4 seasons, but really, there are 2 major mindsets for the year: warm and cold. I suppose that's different depending on where you live. In Texas it's probably hot or hotter. For our friends up north in Canada, it's probably cold and "so cold your balls are frozen to the chair." But anyway, two major seasons and an variable line between them. For some people, winter starts when you see the first Halloween decorations. For some, it's not until you see Thanksgiving turkeys, or even a Santa. For some people it's the leaves changing color, for some it's the first snowfall. Personally, I've liked to go by the first night I'm able to see constellation Orion (but that's just because I'm wierd). There's another way that's become quite personal to me, though. I know it's winter on the first day that my car refuses to shift out of first gear because I didn't let it warm up enough. Thanks, Green Lantern, for being so reliably unreliable.