As W_D says, the climate change bit definitely does factor in when you're looking at long-term data vs. the last 20 years, and you should be looking at the latter. My point was that even with the changes in climate and precipitation patterns, the extremes that you may encounter (such as two big snowstorms in the Wind Rivers, a week apart on Aug. 8 and 15, 2009) haven't changed much in the past 60 years!