The text of the notification is too big. It needs to scale with the notification bar on my basic VS410. At first I thought it was some huge icon, but instead it's part of a number. If you can't do it automatically, provide a way to set the font size.
Also I suggest you automatically default to non-metric when the user's primary location is in the U.S. At least on first install.
Finally, any chance of allowing backgrounds images that change with the conditions to the options? Check out Yahoo Weather--it looks really cool. Too bad they don't give an easy way to get to the useful information like forcasts, making you slide an exact amount or you'll scroll too far.
My perfect weather app would be yours with backgrounds and the notification working correctly.