The Paranal Site Information page provides comprehensive information about the Paranal site, observational information as well as geographical, climate and seismical data.
On the page Astroclimatology of Paranal you will find various links realted to the observing conditions and data for Paranal.
Detailed Weather Information and Weather Forecasts can be helpful for planning and scheduling observing runs. The information including actual, short term and long term weather forecasts and as well satellite images.
The ESO Ambient Conditions Database lets you query the weather database for La Silla and Paranal since Aug.1998