I chose Boulder as it has very good record keeping(and it goes way back) and is a good bellwether for the state, plus a number of key government climate labs are based here. So its a solid data point. If I had more time I would crunch numbers from a array of other cities like Breckenridge, Aspen, Colorado springs, and Grand Junction, the former two may or may not have great data from before the 1950s'.