The Pacific Northwest is lovely in September. Seattle has already been mentioned. I'll add my recommendation for Vancouver. Both cities have a lot of rain year-round but September seems to be the driest month out in that neck of the woods (I don't know what the weather almanac says, just basing that on my experience), nice blue skies and comfortable temperatures. There are plenty of really interesting day trips to be found from either city. Of the two, Seattle is probably the more affordable, especially with the current US-to-Canadian exchange rate, but with a little homework you can find plenty of low-cost ideas for entertainment in either city as well as reasonable prices on meals. Accomodations in Vancouver can be quite expensive so if your travels take you there, look into air-and-hotel packages or hotel packages with added amenities such as free wifi (if you don't already get that from hotel status). The Experience Music Project in Seattle is one of my favorite attractions anywhere.