Here are a couple charts I put together with average first frost dates:
Everything is lining up well for a perfect night of radiational cooling. Skies have cleared out, dewpoints have lowered, and we have no significant pressure gradient either up/down the Willamette Valley or east/west through the Gorge. So no stirring of the wind. Those dewpoints are a little higher than I’d like for low temps in outlying areas to drop into the upper 20s. But some drier air above should work down during the night, plus some moisture will condense out as either fog or dew. So my forecast of 37 at PDX and the coldest spots (SPB & HIO) at 28-29 SHOULD be okay. We’ll find out in the morning.
Chief Meteorologist Mark Nelsen
FOX 12 Weather Blog 
I moved my avocado around to the back yard and pushed it up against the back of my house. Hopefully it will stay warm enough back there, but I think I’ll throw a blanket over it for good measure.
Best I can do.
It was 43 at the Clackamas County Sheriff’s Office Public Shooting Range when I drove by about 45 minutes ago.
41F at EUG airport
51F at PDX airport
Consider average drop of temps 1.2 deg/hr from here…should be 28-29F tomorrow morning…so looks like a good chance of tying record…
As for PDX…back on Oct 24 2002 it was 52F at this hour…dewpoints a bit higher then than now..and it still got to 34F the following morning…so I think PDX could tie the record tonight as well.
getting cold here 39 elvation 600 feet
Well, I’m not rooting for frost, but I am anticipating frost. So I’ve got protection on all my tender crops…… ‘Tis the season!
2009-2010 PDX had the first freeze on 12-2-2009
2010-2011 PDX had the first freeze on 11-21-2010
Rooting for the frost! Currently 47.6°.