Umbrella Today? is a super simple site that falls into the category of “I wish I made that.” You put in your zip code and it tells you weather you need an umbrella in a simple yes or no. Funny enough I left this comment in response to a post about the same idea involving pants a few weeks ago, “I actually think there could be a whole series of these. I wanted one specifically for umbrellas as well. Shouldicarryanumbrellatoday.com …”
They came up with a better domain than me (and I still think you could come up with a whole series of these for different stuff).