Most varieties of cannabis will begin flowering once the duration of darkness is 10 hours, not 12. 12 hours of darkness begins after fall equinox, so an outdoor crop wouldn't begin flowering until the last week of September if a full 12 was necessary. I live near the 44th parallel, and every variety I've grown outdoors has started flowering by mid August when the light/dark is 14/10. Some start earlier than that. There was one type called auto affie (for autoflowering afghani) that would begin flowering with even a single hour of darkness. I'd transplant it outdoors at the beginning of June and harvest it in early August, then transplant another outside for an early October harvest.
Also, it's not hard to produce 2 outdoor crops a year if you use a light deprivation greenhouse to control photoperiod. Oregon's rules take that into account. A 2 crop garden permit allows half the square footage of a 1 crop permit.