An automatic door seal seals the gap between the lower edge of a door and a threshold. The seal is magnetically actuated so as to move downward into sealing engagement with the threshold when the door is closed and raises out of engagement when the door is opened. A transmission assembly converts horizontal movement from the magnetic force into vertical movement for the seal. Springs provide a reset force when the magnetic force is eliminated so as to retract the seal strip whenever the door is moved from the closed position.