GNOME Shell Weather Extension by Neroth is a fork of the original GNOME Shell Weather Extension, which compared to the original, comes with multiple locations support, you don't have to manually enter a WOEID and bug fixes (the weather information seems to load a lot faster with this extension). It displays the current weather conditions along with a forecast for today and tomorrow on the top GNOME Shell panel.
The extension lets you easily search for a city within its settings, so you don't have to enter any WOEID from weather.yahoo.com like in the original version. From its settings, you can also configure the temperature unit, wind speed unit, position on the panel, enable/disable: symbolic icons, show temperature on the panel and conditions on the panel.
It supports adding multiple locations, but it can't display the weather for all in the same time and you must click a city in its preferences to get it to show up on the top GNOME Shell panel.
GNOME Shell Weather Extension by Neroth is not available on extensions.gnome.org, but it can easily be installed in Ubuntu. But before installing this fork, make sure you've removed the original GNOME Shell Weather Extension, or else there will be a conflict:
sudo apt-get remove gnome-shell-extensions-weather
Then, add the PPA and install GNOME Shell Weather Extension by Neroth in Ubuntu 11.10, 12.04 or 12.10 (I've only tested it on Ubuntu 12.04 with GNOME Shell 3.4) using the following commands:
sudo add-apt-repository ppa:gnome-shell-extensions sudo apt-get update sudo apt-get install gnome-shell-extension-weather
There are packages available for Arch Linux, Fedora and ALT Linux too - check out GNOME Shell Weather Extension by Neroth on GitHub.
Once installed, restart GNOME Shell (ALT + F2 and enter "r" or log out and log back in) and activate it using GNOME Tweak Tool.