The current MythWeather in Fiesty no longer works as MSNBC has changed their data format. In order to get a working version of MythWeather you must build from the new mythweather-revamp source, which I must stress is beta code.
Get All Requirements
Get everything that may be required to build MythWeather
sudo apt-get install build-essential sudo apt-get build-dep mythtv mythweather
Get the perl modules that are missing
sudo apt-get install libxml-simple-perl libsoap-lite-perl libdate-manip-perl libimage-size-perl libgraphics-magick-perl
Get the Source
If you don't have subversion installed
sudo apt-get install subversion
You need to check out the MythPlugin source from here
sudo svn co http://svn.mythtv.org/svn/branches/release-0-21-fixes/mythplugins
Compile the Source
cd mythplugins sudo ./configure --disable-all --enable-mythweather --prefix=/usr sudo make sudo make install
Fix Script Permissions
Sometimes the Perl scripts do not get execute permissions, we need to fix this
cd /usr/share/mythtv/mythweather/scripts sudo chmod +x *.pl
MythWeather should now be installed, it is time to enter your MythTv Frontend in order to configure MythWeather.
Utilities/Setup -> Setup -> Info Center Settings -> Weather Settings -> Screen Settings
Choose the screens you want to show up in MythWeather, after choosing a screen make sure you move down to the Active Screens and choose a location for each one. When you are done you need to save your data by hitting your menu button, default is 'M'.