I'm not on that side of the mountains, I'm about 45 min. north of Seattle. I went to school at central in Ellensberg for my last 2 years. My first winter on the east side of the mountains and last, 1978. They had the worst Ice storm in ten years. The next winter I did my student teaching on this side of the mountains. Yes, Spokane can get so cold. My oldest son is in Pullman right now, he likes it. Not for me!
Anyway keep us posted on your planter.