From ThinkGeek.com:

" This umbrella has been injected with some wonderful technology in the handle. A built-in wireless receiver gets a daily weather forecast from Accuweather.com, and blue LEDs will flash to let you know if the forecast is rain or snow. The LEDs located at the bottom of the handle will flash in proportion to the chance of precipitation for your area; if there is a 100% chance, it will flash quickly, and if a 10% chance, it will flash slowly."

For the poor saps who live in places where it rains, it seems like it would be super cool to leave this hanging by the door. Then on the way out, just check the light to see if you should bring it along or not.