It would help if you said what weather app you use, on what version of Ubuntu.

I am using Ubuntu 10.04 on a laptop at this moment, and I use the weather option
on the clock. It has worked every day in the past week. Is there any chance the
source of your weather information has shut down? I get the temperature from a
nearby, small, private airport -- which has been sold to a developer who will
build houses there. Someday soon I will need to change my "location."