Snowstorm is a free weather widget for Android phones, and it currently supports Android 1.5 - 2.1, and most screen size.
Snowstorm was developed since I couldn't find a good weather widget that was free, supported vital configuration options, and used yr.no as a weather source.
The widget does currenty support the sizes: 4×1, 2×1 and 1×1. See the configuration page for information on what you can configure.
I hope that the weather widget works in most larger cities in the whole world, and possibly also in smaller areas.
There's a short guide that describes how to use Snowstorm.