Weather Underground has a very nice, iPhone optimized webpage. You can find out humidity, dew point, visibility, sunrise, sunset, detailed forecasts and warnings. It even has the large iPhone “slider buttons” for some of the settings such as animating the radar.

Another smart element is the #id links at the top of each section: “Current”, “Radar”, “Forecast” and “Warnings”. Not only can you can skip around between the sections, but each perspective’s section is identified by their title being in yellow (even if you scroll down to it).

I usually just use the Yahoo weather widget to check what the temperature will be and if I can wear flip-flops or not. But I’m adding this to my home screen for when I ever want to check anything more than just temperature.