I'm on the other side of the mountains where it gets lot colder. My birds have shelter from the wind and rain, if they choose to use it, and they are fine. Your birds just need someplace where they can get out of the wind and rain. It doesn't get all that cold in the Willamette. It's not like you are trying to raise them in Northern Alaska, If you are really worried, build them some enclosed nest boxes and fill those 1/2 way with loose straw. The birds get inside and it holds their body heat so they can warm up the space.
I've got my coop, which stays nice and dry and has 2 windows and a small entrance door for cross ventilation. Then that lets out into a secure run that is covered complete with a tarp, so that stays dry, too. Then during the day, I open that secure run and they can go into a large fenced orchard.
If your new birds are quite small, they probably should never be out in any place without a cover. Small birds could be killed by crows, raptors, magpies, or seagulls.
