I'm using the weather-plugin 0.8.1 with Xubuntu 12.10's xfce 4.10 desktop. When I start the desktop and watch the cpu time of the plugin, it changes only when actively using the plugin. When the time passes a whole hour (e.g. 15:59 -> 16:00) the cpu time for plugin goes constantly up every 1 or 2 seconds. It seems the plugin tries to update its weather data but never finishes it correctly and therefor keeps polling. The popup or the details window show the condition from 16:00 to 17:00, that means something was updated. For the temperature its shows: "values at 16:00" which would be correct, but freshly started it shows the end of the interval (in our case it should be 17:00), that means something was not updated. If I do now a manual refresh, the temperature switches to "values at 17:00" and the polling stops (that means the increase in cpu time goes back to normal).
Thanks for analyzing this, but I think your cpu load problem might go away if you update to the newest version. Therefore I'm closing this bug, please reopen if you can reproduce it in 0.8.2. Because of the data provided, on a fresh update only the values at the end of the interval can be shown (data before that point - 17:00 in your case - is not available). If possible, the plugin will show data at the begin of the current interval (which would have been 16:00 in your case). Old values (before download) currently are not kept in memory. I will try to improve this a bit in one of the next updates.