The story is supposed to take place in 1935. Depression glass is used throughout the film. Most of it is correct, such as the Madrid pattern in amber used in the opening shot which was made by Federal Glass Company of Columbus, Ohio between 1933-1939. However, in a kitchen scene on top of the stove there is a pair of Waterford pattern salt and pepper shakers. This pattern was made by Hocking Glass Company (now called Anchor Hocking) between 1938-1944.
When the sheriff is seen in the rail yard, the highway bridge in the background is constructed with precast concrete beams that had not been invented until many decades after the 1935 setting of this film.
When the children run out of Mr. Will's room (after playing his phonograph), Frank leaves the desk lamp on. When Mr. Will discovers the record is scratched, the lamp is off. Since he is blind, he would not have used, or changed, the lamp.
In the final credits, the real name of Otis the fiddle player in the band is wrongly spelled as Cliff Brunner. It should be spelled Bruner. He was a well-known fiddle player with Milton Brown's Musical Brownies.
After the tornado and when they emerge safely from the root cellar, although there's debris everywhere nothing is wet. It will always rain in a thunderstorm big enough to spawn a tornado so everything should be soaked.