Something that comes up periodically is weather planning for tours beginning sometime in the future relatively distant future. Local/short-term planning is a completely different animal and can usually be handled with local radio/television forecasts.
Something that I've had relative success with is using www.wunderground.com's history function. For instance, http://www.wunderground.com/history/...lyHistory.html is the page for Feb. 2010's weather in Tallahassee, Florida. Temps (max, min and avg/day), wind (max, min, gusts), precip and other data is included. The most useful compilation/display of the data is near the bottom - even downloadable as a comma delimited file for incorporation into either your own personal database or an Excel spreadsheet for future manipulation/reference.
The one unfortunate thing is they don't have wind direction data.
Speaking of which, wind rose data is available for the US from a few sites. Unfortunately, it's generally either an overwhelming amount of data from a huge number of sites or it's very site specific - as in a single location. What I have yet to find are state-by-state or regional prevailing winds charts/maps on a month-by-month or season-by-season basis. Does anyone know of such a resource?
Does anyone else do similar weather research in their tour planning? What resources do you find most useful - especially if one does not rely on the ACA maps?