Gary Gragg has explored outlying regions of northern California for oddball avocado plantings, and he's showcased several on his YouTube channel. He has one video of a grove of trees in Shelter Cove, that he sold to a guy there. I have seen comments on another channel someplace, from a resident of Crescent City who had a few planted outside. So there are microclimates along the coast even farther north than S.F. that have been successfully colonized.
Avocados can survive fine in cool climates, but they prefer to flower above 75 degrees. The shorter seasons to harvest can become a problem the further north you travel, because the fruit needs a long time to hang on a tree and mature. It might be possible to find a microclimate in Oregon that doesn't freeze a tree, but that might also involve waiting until May before flowering, leaving too little remaining time for the fruit to fatten up. That's not such a problem in Southern California, where fruit don't face any hard freezes and can hang on the tree through the winter until an owner feels like picking.
Just as an extreme mental example... Ocean Shores in Washington State rarely has freezing nights, despite being at the same latitude as Olympia. But the average high temperature doesn't get above the low 70s, even in the middle of summer. A tree planted there might live... but it also might never flower at all, and would just be something to look at.
And then there is the matter of the long cloudy days from October to April. I would expect in reality, a tree would drop its leaves from lack of light - even if the frost was not killing it outright.
I guess in the end, you can fool mother nature a little bit with microclimates. But you can't fool the sun!!