Hi Miriah:

First, take note that it is important to plant rhododendrons in a north or east facing sun/shade exposure. Rhododendrons need protection from the wind and direct afternoon sun. Because rhododendrons have shallow, fibrous root systems they need ample water during the summer. You can apply a layer of mulch to control weeds and conserve moisture.

That being said, the P.J.M. rhododendron is a good performer in Central Oregon. This is one of the cold hardy varieties for this area.  The link below will take you to more information on that variety.  When you are on that page, you will see a list of many other varieties with links to their page on the right side of the screen.  You can choose from other varieties, if you like.  They just need to be very cold hardy and have many of the same features as the P.M.J.  Another example would be the Rhododendron smirnowii.

P.M.J. Rhododendron

Our local nurseries should only stock very cold hardy varieties.  The link below lists all our local nurseries and their contact information.  You may find it a help in your search. 

Plant Resource Guide

Thank you for your question,