Simple changes could make a huge difference in surviving a tornado. Some estimates put the cost at only $1.50-$2 per square foot for new construction. The anchors and metal clipping connecting all of the wood framing from ground to roof are inexpensive. With existing homes, anchors and clips can be added when a room is renovated down to the studs. If some repair or renovation exposes the framing, you can strengthen the framing connections to resist uplift forces.
All this should apply to hurricanes too. The strongtie website is full of good information.
www.strongtie.com/solutions/high-wind-resistant-construction/building-owners