[InchoateHand]

Dry is key. If you have the equipment to stay dry, then you can probably stay warm. Most established campgrounds, I would guess (though I'm unfamiliar with the Pacific NW) are closed for the season. As such, camping on state land would probably be, technically, illegal.

I'd try to find somewhere secluded, but not totally isolated. Out of visual and aural range, but actually close to other people. That way, if things go wrong, you aren't far, and if things go right, you'll never see or hear from people.

Also, I imagine the you will get substantial enjoyment from planning such an endeavour, let alone carrying it out. Three weeks of batteries. Three weeks of oil lamp. Clothing appropriate for the coldest weather possible in that region. A mix of healthy simple food. A couple notepads to write in, a few choice books---something new, something old.

If you have the time luxury to do this, and feel the need for isolation, go for it. The equipment is a must, but camping in crappy conditions really isn't that hard.