to find a page such as
which says the record Eugene low in September is 32, which doesn't need winterizing concerns but in October it can get down to 19 which means there is some risk if you don't take precautions.
Then you can look at the 'normal' and see that even in February the minimums don't usually go below 37 which says that the concerns are going to be when you have some unusual weather going through.
Then again, that's just measuring 1961
to 1990. Nobody knows, really, what the future weather will be.