read this before:
http://stackoverflow.com/questions/6791273/is-there-a-way-to-combine-the-data-of-google-analytics-and-the-weather

As a google analytics user I want to know if my tracking data correlates with the weather. Are there more people online when it rains outside?

* To what level of location do/can we (need to) aggregate (city, region, country)?
* where is the information dsiplayed: inside GA or on a separate page

google weather api
http://blog.programmableweb.com/2010/02/08/googles-secret-weather-api/