Ok, so the latest version of MythWeather in gentoo as of this date is still having issues because the data from the weather info provider changed in format. So, I decided to grab the latest from MythTV - apparently the mythweather-revamp work has replaced the broken older version of MythWeather.
So grab the latest plugin from mythtv.org's svn repository: (I put mine in the directory mythtrunk-2007-07-22)
# svn co http://svn.mythtv.org/svn/trunk/mythplugins/ mythtrunk-2007-07-22
[snip]
Checked out revision 14027.