Have you ever done something like this:
Get off the Metro to begin the seven-block walk home. By the time you've crossed one street a few drops have fallen. You don't pull out the fold-away hood your jacket comes with -- after all, it's only a few drops -- instead keep walking as the drops become a light rain. Only after another block or so, it gets a little heavier, then a little heavier in another block, so that by the time you're about two blocks away it's coming down pretty good. But you're only two blocks away, and you're already wet, so might as well keep the hood tucked away for the home stretch. And so you do, and you're moderately soaked by the time you unlock your front door.
No real reason I'm asking-- it's not like I did that this evening or anything.