We've been talking temperatures elsewhere on this site, but when we look for real, solid resources, there aren't many that are easily accessed.

Weather Underground thus fills a void.

On WU you can find a full service weatherstation fairly close to where you live and garden (or a station for an area you're interesting in gardening (and living) in).

On the home page, linked below, type in your zipcode. The site will then give you a weather station sort of near you. Go a bit further down the page and you can find other stations in your area. Sharing a zipcode doesn't always mean sharing a microclimate.

I really like the almanac, linked on the first/main page, where I can see and copy charts of the max/min temperatures through the historic records, and the average temperatures. Rainfall and snowfall are also there.

One chart I downloaded for my gardening book has just the temperatures for 2006. The Easter Freeze really stands out. (Temperature almanac, check the previous year and omit max/min and averages.)

I'm northeast of Knoxville so my long term records are from McGee Tyson and I also look at Tri-cities. Morristown would also be useful.

Hope this helps.