Morocco weather

Don't know about the desert, but you should be able to get actual, historical, day-by-day weather statistics for the cities from the website timeanddate.com. I've given you a link for Fes's February 2021 data. I like to look at the most recent five years' worth of data, because conditions can vary a lot from year to year.

https://weatherspark.com/m/31810/2/Average-Weather-in-February-in-Laayoune-Western-Sahara

Looks pleasant

Here's a link that should answer your question: https://www.experienceittours.com/blog/best-time-to-visit-morocco-a-weather-guide/

The desert gets very cold at night as the sand doesn’t retain the heat. Will be warm and pleasant during the day but a warm jacket will be a welcome addition at night. Probably too early for sandstorms...

Our trip was in January 2019, so a month off from your planned February trip. If this helps, Marrakech was pleasant during the day - warm without being really hot. Evenings were mild-to-cool, and even on the rooftop terrace of our riad, it was pleasant at night, maybe low 50’s (Fahrenheit) and above. We did an outdoor market and cooking class one day, and a light sweater in the morning was helpful.

Fes, higher and further north, was considerably cooler. Still not actually cold, but a jacket for the evening was needed.

We had 3 nights in the desert, at two different camps. The days were pleasant, never hot but shirtsleeve weather, but it got really cold at night. We opted for “deluxe” tents, which had a heater and en-suite bathroom, which saved a freezing walk in the middle of the night to the communal port-a-john toilets the “regular” campers used. We wore all our layers for dinner in the camp, and bundled under all our blankets in bed. The cloudless, starry skies are spectacular, but don’t hold in any heat at night.