REQUIRED READING

About this time every year, I re-read the 170 page Garden Guide for the Rogue Valley. It's published by the Oregon State University Extension Service and the Master Gardeners of the Rogue Valley. It's a great resource guide and a good reminder of the reality of gardening here in this inter-mountain region of the West. 
It keeps me from getting ahead of myself with starting seeds too early in the greenhouse. 
One of the most valuable parts of this guide is the table showing the variance in length of growing season between Ashland (151 days average) and the center of the valley where the US Weather Service at the airport is located (174 days average). It shows the difference that elevation makes! (Ashland is 2500' and the airport is at 1330.' 
It also shows the annual rainfall averages which tend to be dramatically different:
Ashland & Medford 19-21" while further west,  Grants Pass is 31" and Cave Junction is 62"! 
At 1900' we are in the "thermal zone" where many times the winter temps are warmer at our elevation than at the valley floor. That is because the cold air drains down off the foothills into the bottom of the valley. It also means that we get less fog since the fog zone is typically below us.  
This information is probably more than you ever wanted to know about the Rogue Valley or as some call our area around Medford the Bear Creek Valley.