"I will say I think its easier to keep down dry in the western US(most of it anyway) than in the east."
By reputation, the weather in the Pacific Northwest tends to be wetter and cooler, and it stays that way for longer periods of time.
In the summer along California's John Muir Trail (somewhat high elevation), it can still get wet, but it tends to be much more sporadic, as Ben suggested. It can be cool, as well, but that varies tremendously with elevation. When a down sleeping bag or down jacket is used for some time, it can be dried on a sunny rock, and then packed for reuse later. At high elevation, there are few trees, so there is less shade to allow cold/wet spots to last.