Consider a one-week trip to Hawaii in the darkest time of winter; supplementation studies have shown that the body can safely absorb and store 100K IU, that it takes about 2 months to deplete such an amount. Your skin produces 20k IU in 30 minutes on a sunny day at the beach (wearing a swimsuit). If you're in the PNW (or central Europe at the Southern German border) your skin cannot produce vitD from October through April because of how low the sun is in the sky even at its zenith.

> However, it is going to be hard to leave the PNW because I love hiking and backpacking.

I'd argue that the desert southwest is a great place for hiking though you obviously have to plan around the extreme temperatures. But the mountain ranges tend to be significantly cooler and a viable option in the summer. The big downside, more for backpacking, is that you either have to: carry all your water, stash water ahead of time, or refill at springs that may be unreliable.