And it will rain whenever it wants here. There are no safe dates that will guarantee a rain free experience. But your best bet is August or September. And I wouldn’t worry about bugs very much. I camp all the time and the only time we have had a intolerable amount of mosquitoes was when we tried camping near a pond. The critters like stagnant bodies of water.
yep, john got this one right. in addition, as soon as you get east of the cascade range, up into the high desert plateau that covers the other 2/3rds of the state, it’s a lot drier in general.
Oregon is a big place with diverse micro-climates. The coastal range versus the Cascades versus Bend versus Steens (the SE corner, the area in the lower 48 states with the least light pollution!). It’s all good, but you pretty much should go prepared by any kind of weather anytime.