The short answer
Sunny and mild by day, cold at night. January highs are about 19 °C and lows about 6 °C, the coldest of the year, with some rainy days. Snow covers the High Atlas, visible from the city. It is one of the quietest months for sights, though the marathon weekend and a Moroccan school break bring crowds.
In more detail
Our climate table agrees with the published sources on January: a high of about 19 °C and a low of about 6 °C. Desert nights near Marrakech and in the Sahara fall near freezing. The sun sets at about 17:50 in mid-January, and the light on the Atlas snow at the end of the day is one of the sights of winter.
Three dates shape January 2027. Yennayer, the Amazigh New Year and a public holiday since 2024, falls on 13 or 14 January; the exact day needs checking. The Moroccan school break runs from about 24 to 31 January 2027. The Marrakech Marathon, its 37th edition, is on Sunday 31 January, with roads closed on race morning.
The Tizi n'Tichka pass to the south can close after heavy snow, most often in January and early February, so leave slack in a Sahara plan. In the city, January is good for palaces, museums and long lunches in the sun.