Other mistake: If the show takes place in May, when Lincoln is scheduled to be executed, why is it snowing?
Suggested correction: It does occasionally snow in such months. There is no rule about weather being certain. It's just what we consider usual for each season, e.g. winter = cold. Characters even comment on very "variable" weather in state.
Other mistake: Between season 1 and 2 the opening there is a shot just as Dominic Purell's name comes up that features a blueprint. On the blue print, there are 2 distances visible - 7' 15" and and 23' 15." There are only 12" in a foot. (00:04:00)