Stupidity: In the opening, it's surprising that Jo and her family have to actually go outside and run even a short distance to get to their cellar. Farm houses, especially in tornado prone areas like rural Oklahoma, would typically be built overtop of the cellar, which would be accessible from inside the house. Furthermore, Jo's cellar door seems to be secured with what seems to be little more than a latch much like those used for restroom stalls! Not very practical for a door intended to protect the interior from outdoor elements.
Suggested correction: Their storm cellar is made of an old septic tank, which is very common to do. It's half buried into the ground so it provides maximum protection, unlike under the house because an F5 tornado would simply rip the entire house away, removing all the protection the cellar would have had. Also the door has several latches, not just one.
A cellar under the house would likewise be buried into the ground, often more than halfway, so it would offer just as much protection, if not more. Looking at the scene again, the door has two latches, both the same size and woefully insufficient.
