The desert demands a different mindset entirely. Daytime temperatures in the Erg Chebbi area peak above 40°C in July and August — but even in April or October, nights drop to single figures after 10 pm. The ground between those two extremes is a windswept, sand-blasted environment that will find every gap in your gear.
Leave your main luggage in the tour vehicle and bring only a small overnight bag to the camp. Camps provide blankets and pillows; you do not need a sleeping bag. What you do need: a warm layer, a head-covering scarf, closed shoes, a headlamp for nighttime dune walks, and a dry-bag or ziplock for your phone. Fine Sahara sand gets into everything — lens caps, USB ports, every pocket.
If you are booking a private guided tour, your driver can usually advise on conditions for the exact dates you are visiting. Experienced guides know when a wind warning changes the packing calculus.