After pondering my own question for a while, it occurred to me that there must be historical statistics on the frequency of thunderstorms and the prevalence of cloud cover for different areas of the country. Sure enough, after some stumbling around on Google, I came up with this site:
Weatherspark dataOnce you click on a state, various cities (mostly with airports) pop-up – and then you can look at the data for each town. There are really good graphs showing the likelihood of precipitation throughout the year, the extent of cloud cover, etc.
So after all that, it turns out that the best areas for clear, dry, skies in mid-August are eastern California and northeastern Oregon! I am surprised, only because we have had trouble in past years in the Eastern Sierra with monsoonal clouds and thunderstorms. But apparently, the statistics are in our favor, so we will probably be heading back there this August for the meteor shower.
