A Short Story
My zsh prompt starts with a cute cloud. I have nothing against clouds. I like clouds... But this one was a little bit useless. So I said to myself: Myself, Why don't you put the current weather condition in your prompt? And that's how this happened.
Go to http://www.wunderground.com/weather/api/ to get your API key (Its free for <=500 queries in a day) Set APIKEY env varible to the API Key you've obtained.
The script connects to wunderground and asks for the weather for a particular zipcode.
Personaly I have cron job running every 1/2 h storing the weather into my $WEATHER env var... But you could do something useful in many other ways.
The code is the documentation ;)