If you want more info on the weather in Silverymoon and the Silver Marches, check out WotC's aptly named book: The Silver Marches. It has lots more very useful info (although I think the adventures are a waste of space and those pages could have been used better).
And if you want the weather info from said book completely automated, I can only pimp my own Excel genereator. ;-)
It calculates the weather for an entire year, for all 3 regions.
A new version that includes a calander and other stuff is nearly ready (and has been for a while now) I just need to type up the changes and add a how to page.