I don't think there are too many instances that you wouldn't have a pre-warning - except for a tornado. It doesn't happen instantly. We were near a major fire recently and homeowners packed their cars and drove them around like that for a couple weeks before the pre-evacuation was lifted.
Ourselves - we also kept a 'GO' bag packed and setting by the RV door - easy to grab in case of fire. We moved it to the bedroom at night - ready to toss out the window. It got to be a habit and we never thought of forgetting it. We even took it with us when we had the motorhome in for servicing. If boondocking and we went off exploring - it went with us.