How far do you anticipate needing to drive in a wildfire evacuation? I think 100 miles should be plenty to get to safety, but I guess you need to think about the next few days in wherever you are stuck.
Where I'm at, 250 miles wouldn't be crazy. I have to drive an hour to see a stop light and in the summer, that city will be booked full. The next city is isn't any better, but at least I'd have family to crash with.