All weather data is suplied by Meteo France and is on a internal F1 team intra-net.
However, you can find other weather radar sites that give you the data for the track on the internet.
The reason that all the teams have the same wether data is for cost reasons, up untill 2004/2005 all the teams used to have diffrent weather streams, costing them millions, in 2004 6 teams signed up to a "universal information aggreement" and all pooled the weather info and other various data from outside agencies. It workds so well that from 2007 all teams had to use a standardised data system for weather.
Heres the system that the FIA probably use:
http://www.mfi.fr/en/
Id recon this is only accessable to the teams.