Tornado threat may be sufficiently mitigated just by digging a [dry] hole in the ground, and getting into it whenever the sirens go off. If you have enough money, you can bolt a steel box to your foundation and hide in that instead.
We can actually build structures that can withstand [the most common] tornadoes, without adding too much to the cost of construction. Basically, monolithic concrete shell structures over inflatable forms are effectively "tornado proof", without additional engineering.
The nasty natural disasters in the Midwest are not just blizzards, but freezing rain storms. A coating of ice an inch thick on everything is guaranteed to take down trees and power lines, and make all roads completely impassable. You get up to a week without civilization. For example, if your furnace catches fire, you can call 911, and later find out that the first fire truck they sent out slid off the road into a ditch on the way to your house, and the guys that finally showed up two hours later were the second truck, sent over from the next township (true story). On the Great Plains, it's drought and brushfires. You get to spend a season watching everything turn brown, and then your town burns because some jackoff threw a cigarette butt out of his window on the highway, or because lightning struck the wrong spot.
Thanks to modern meteorology, tornadoes are just much less a threat than they used to be. They might pick off a person here or there every season, but when they do, there will always be neighbors around ready to help. They just don't wipe out an entire city, leaving everyone essentially on their own, because they are all (sometimes literally) in exactly the same boat.
And that's exactly why I am comfortable living in an area where the major natural disaster threats are tornadoes and flash floods.