This reminds me of goingtorain.com which went offline when Google cut off their weather API access surrounding the iGoogle planned shutdown. I don't know why the developer of that service didn't just switch to Yahoo's API, though I suspect it was because that was a hassle.
There was also http://www.doineedajacket.com/, but that seems to have gone ad-crazy to the point where I can't find the result.
I noticed an oddity when switching between metric and Imperial/US measurements. Metric gave me 94% humidity and 23 kph while imperial gave me 88% and 9 mph.
Whearther. Check
Location. Fail
The geo-location isn't 100% accurate, but you can type your location manually or choose one from the suggestions list below.
I didn't type because I'm on an iPad, and we all know how good is to type on screens. Maybe the app should acknowledge the fact that it isn't very good pinpointing the user location, and based on what it already knows, suggest neighboring places.