One more thing to note, especially in reference to this extreme temperature swing of 50 degrees we had.....big temperature swings were also quite common in the late 80s and early 90s.....1989 and 1990 show up a lot on Roger's list of the biggest temperature swings, so that may be another repeating cyclical pattern, along with going into drier years than we've been used to and less humidity (specifically applies to the summers.)
Might want to look into solar cycles too, as the early 90s were near the peak of solar heating.