Marrakech is a true “year round” destination with almost guaranteed warm temperatures.  We visited in April and stayed at the Sofitel which is within walking distance of the key sights.
The top 10 things to see and do are:-  visit Jemaa el-Fna which is the pulse of Marrakech, Jardin Majorelle, a local Hammam, Koutoubia Mosque, Saadian Tombs, Tanneries, Museums, Old Medina Souks, Ben Youssef Madrasa and stay in a delightful Riad.  Whilst you’re there make sure you try the street food!