The best time to visit M'Hamid is October through April. Spring (March–April) is particularly beautiful: the daytime temperatures are warm but not brutal, the desert plants flower after any winter rains, and the light is clear. Summer (June–August) is extremely hot — daytime temperatures routinely exceed 45°C — and most experienced desert travellers avoid it. The overnight camel trips that make M'Hamid worth visiting are genuinely dangerous in midsummer heat.
Winter nights (December–January) can be cold, dropping close to freezing in the desert, so bring warm layers for overnight trips even if the days are mild.
The Monday souk in M'Hamid brings in traders and nomads from surrounding areas and is worth timing a visit around if you can.