Modern down jackets are usually water resistant to some extent. Ive got a Mountain Hardwear Subzero Jacket, and the shell is made of Conduit SL, which is the same material they use on their bivi bags. Ive had no problem with it getting soaked. The problem with down IMO, is that its too warm for the temp range you described. Personally i wouldnt wear it above zero degrees.
Have you considered getting a jacket and paring it up with a hardshell? It could be down, wool, fleece, other synthetics, etc...The choice is yours. Throw on a hardshell, and you wont have to worry about rain or wind.
Ive been warm in zero degrees with long sleeve Helly Hansen, microfleece, wool sweater and a hardshell. And that was right after i crawled out of the sleepingbag with no activity to aid in keeping me warm.