squaredesign

WX Weather displays data from a Personal Weather Station, retrieved from the website <a href="www.wunderground.com" rel="nofollow ugc">Weather Underground</a>.
to use this for your own Weather Station, you need to submit your data to Weather Underground, and you know your Weather Station code. to find out more about how to do this, visit <a href="http://www.wunderground.com/weatherstation/about.asp" rel="nofollow ugc">Weather Underground’s Personal Weather Station Page</a>.
data is cached locally in your WordPress install, so it only makes one request to Weather Underground every five minutes.

WX Weather Widget

WX Weather is a WordPress widget designed to display data from a Personal Weather Station (PWS) in your blog sidebar.

Theme Egg

This is Weather Forecast widget plugin, You can add widget by installing this plugin. 
After Installing this plugin go to Appearence>>Widget and add widget to your sidebar.

Weather Forecast

This is Weather Forecast widget plugin, You can add widget by installing this plugin.

WX Weather Widget vs Weather Forecast