I would love for my wife and I to take a trip to Colorado, Washington or Oregon to view a meteor shower there Aug. 11-13. It’s impossible to make a specific forecast this far in advance, I realize, but which of those areas would have a high probability of a clear sky then?
Interior Washington is your best bet, the area in the “rain shadow” of the mountain ranges in the western portion of the state. Places like Yakima offer the best chances of a clear sky in August. Yakima, for example, averages only two days with rain in August.
A “rain shadow” is an area that lies to the lee of a major barrier such as a mountain range. Prevailing winds lose moisture (through precipitation) on the upwind side of the range, then dry out as they descend the downwind side. Clear skies are the result. Rain-shadow areas in Oregon and Colorado offer similar conditions, but Washington is best.