Here is a graph of the weather in Marrakech throughout the year courtesy of the BBC

Marrakech weather - Sunshine all year round

Marrakech weather is consistently sunny, making it an ideal year-round city break destination. Average sunshine hours in Marrakech never drop below 7 hours a day and reach a steady ten throughout the summer. Most visitors and residents consider spring, early summer and autumn to be the best time to visit  Marrakech. March to June and September and October have some of the best weather in Marrakech, avoiding the extremes while being warm enough for hotel swimming pools. Average temperatures in Marrakech vary widely between night and day. Winter weather in Marrakech is mild and generally sunny by day but prepare for the winter nights, which can be very cold.

Marrakech weather - Prepare for sundown
Temperatures in Marrakech are markedly different at night, particularly in the winter, when temperatures can suddenly drop when the sun disappears. Temperatures in Marrakech can vary between 5º and 18º in December and January. Rainfall in Marrakech is virtually unheard of in June, July and August. Marrakech rain is evenly spread throughout the rest of the year. You will be unlucky to have rain in a short break weekend in Marrakech but you should bring shoes for muddy conditions in some parts of the city.

Marrakech weather - Hot dry summers
Marrakech weather is notable for its high temperatures in summer. Summer maximum temperatures are over 30º. Do take care not to over exert yourself in the hottest months. The weather in Marrakech in summer is hotter than the weather in Morocco beach resorts like Agadir, Essaouira, Tangiers and Taroudant.