Ubuntu 10.10 Maverick Meerkat will remove the current clock applet and replace it with a very simplified applet which you probably already have if you installed Unity in Ubuntu 10.04 Lucid. If not, this is how it looks:
As you can see, it's just a simple clock, with no weather conditions.
But a new Weather Applet was released on Launchpad (pictured in the beginning of the post) which comes with indicator applet support, lots of configurable options and notifications - which you can set to give you severe weather alerts or just weather conditions change:
Weather Indicator Applet also comes with an extended weather forecast:
Being still experimental, there are bugs: even though I've set the temperature unit to Celsius, it displays the extended forecast in Fahrenheit. Also, the panel applet doesn't seem to change (it shows a sun while it's 12:07 AM here).
To install the Weather Indicator Applet in Ubuntu 10.04 Lucid Lynx or Ubuntu 10.10 Maverick Meerkat, use the following commands:
Update July 11, 2010: I've updated the last command since 'weather-indicator' became 'indicator-weather'.
sudo add-apt-repository ppa:weather-indicator-team/ppa sudo apt-get update sudo apt-get install indicator-weather
After installing, go to Applications > Accessories > Weather Indicator Applet and when prompted, simply enter your location like so:
Update January 16, 2011: I've replace the old PPA (which no longer exists) with a new PPA that provides new versions of Weather Indicator!