I have an interior bath room..and have had to get covered in the tub only once in almost 20 years..No basements in Texas where I live. If it’s a big one I and my neighbors survive by the grace of God.
My son and his wife survived the 1979 F4/ some say F5 in Wichita Falls TX. Many did not.
Do you pull a sheet of 1” plywood over top, for cover in the tub? What do you use to cover with?