Weather: "the atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation" (via WordNet)

Current Weather and Forecasts:

• Weather Underground Ann Arbor forecast
• Weather Underground Ypsilanti forecast
• Cumul.us unused weather aggregator + prediction market for Ann Arbor
• Wolfram Alpha (!) Ann Arbor forecast

Real time weather stations

• C4874 at Rudolf Steiner High School on Pontiac Trail
• KARB at Ann Arbor Municipal Airport
• KYIP at Willow Run Airport

Nice weather:

• Clear Sky Chart tells you when to go outside, or to the Angell Hall Observatory

Bad weather:

• Ann Arbor and Ypsilanti area DTE Power Outage Map
• Spring:
  • Watch the Huron River flood
• Winter:
  • School closing list from WWJ
  • Wait until it stops, then go Sledding