WP Cloudy is a powerful weather plugin for WordPress, based on Open Weather Map API, using Custom Post Types and shortcodes, and much more.
ZigWeather gives you a multi-widget to show weather on your site.
Give your WordPress site wind.
Get your favorite city weather in a widget with Yahoo! Weather. Easy to customize and support multi-widget.
The Windspeed Converter gives you the possibility to insert a converter via widget or shortcode into your site.