In the southern city of Guelmim alone, 13 people were killed by a flash flood that roared through a dry river bed, reported the Interior Ministry in a statement carried by the national news agency late on Sunday.
There has also been flooding around the resort city of Marrakech, highly popular with European tourists, with roads being cut and tour buses briefly stranded, according to local media.
The ministry added that at least 18 people have been reported missing.
The press has also reported that dozens of homes have been swept away and bridges cut by the flooding.