I've a feeling Joel Spolsky's comment on the 80/20 rule applies to weather sites: "80% of the people use 20% of the features. [...] Unfortunately, it's never the same 20%."
With weather it should be pretty simple. Temp and odds of precipitation are the two biggies. Have nice radar/sat images/loops easily accessible. Put the other stuff farther down.
That's where the good radar/sat stuff comes in. Wunderground does a good job at this, their stuff is very customizable. Lately I have been digging the Dark Sky app, weather at its most simple. It tackles very short term forecasts with specificity (it's going to rain in 8 minutes). I live in Florida so I know it's going to be hot, the only question for me is rain.
