Which U.S. states are the most...

This is a tough question, mostly because there is no scientific definition of temperate as you’re using it. What we can say is that, in the United States, as locations approach the equator, the average and mean temperatures rise. Warmer average temperatures mean there is less likelihood that ‘true seasons’ will occur, so one could generally say that the middle area of our country is where seasons remain very defined, but somewhat moderate. However, these rules are not without exception. As altitude increases, temperatures can drop. There are locations where seasons are very localized, due to differences in altitude, for example. An area that has less distinct seasons could be adjacent to regions that do in fact experience leaf-changing in the fall. Fall weather conditions favoring formation of brilliant autumn color are warm sunny days followed by cool, nights with temperatures below 45 degrees F.