The Souss valley gets hot in summer — July and August temperatures regularly exceed 40°C inside the walls, and the midday hours are genuinely unpleasant for walking around. Spring (March to May) and autumn (September to November) are the ideal windows: warm enough for comfortable evenings, cool enough during the day for exploring on foot or by bike.
Winter is mild and often sunny, with temperatures in the mid-teens. If you're planning to trek into the Western High Atlas or Djebel Sirwa from Taroudant, spring and autumn are again the best choices — summer is too hot in the valley and potentially problematic on higher routes, while winter brings snow to the passes.
The Souss plain is famous for its orange and almond blossoms in February and March, when the groves around the walls are at their best.