Morocco has a wide range of climate conditions. The coastal regions generally have an all year mild climate, the Atlas mountains can be cold and wet in spring or even in summer and the desert is hot and dry nearly all year. Here the temperatures differ a lot between day and night.

Regarding the climate spring and autumn are the best times to go.
Midsummer can be lovely on the coast or in the High Atlas, as well as winter can be nice in Marrakech or more south.