The best time of year to drive out to Merzouga and sleep in the dunes

Take the year in order. What follows is the shape of a season in the south of Morocco rather than a set of dates, because dates belong to the listing calendar and to the sky, and neither of them takes instructions from a web page.

Spring. The best combination on offer. Days are warm without being heavy, the nights in camp are mild enough that the cold is a pleasant detail rather than the story, and the valleys on the road — the Dades Valley, the palms along the river below Ait Ben Haddou — are green. The pass over the High Atlas is straightforward. If you can choose your month, choose one of these.

High summer. July and August are hot in a way that changes how the day is organised rather than whether it happens. The ride out over the dunes moves towards the evening, the middle of the day becomes shade and water, and the drive itself is long hours in a vehicle in real heat. People do this trip in August and come home glad they did; they also come home telling you about the temperature. Bring more water than you think and a cover for your head.

Autumn. The other good answer, and the quieter one. The heat has gone out of the middle of the day, the light gets longer and lower through October and November, and the dunes at Erg Chebbi take shadow beautifully in the late afternoon. The valleys are drier than in spring. Whether that is a loss depends on whether you came for green or for sand.

Winter. A different trip wearing the same name. Days out at the dunes can be pleasant and bright; the nights get cold quickly once the sun is off the sand, and the pass over the High Atlas carries snow on the tops. There are also days with cloud and with sand in the air, which is simply what winter in the desert includes. Come in January by all means — but pack as if you were going somewhere cold, because for twelve hours out of twenty-four you are.

Most pages about timing here talk about the daytime. That is the wrong half of the day to think about, because the daytime is spent largely in a vehicle with a window, and the night is the part you actually bought.

What the night is. The camps sit behind the first crest of dunes, which is why no ordinary car reaches them and the last stretch is a camel or the operator’s four-wheel-drive. You are out of sight of the road. Dinner, then the sand, then a tent. Sunrise over the dunes happens where you are standing rather than somewhere you drove to, and that is the single thing that no shorter version of this trip can give you.

What temperature does to it. Sand holds heat badly, so it loses it fast. In spring and autumn that means a warm evening and a cool night, which is comfortable. In winter it means a pleasant afternoon and a genuinely cold few hours before dawn. In high summer it means the evening is the good part of the day, and the tent is warm later than you would like.

What to bring, by season. For spring and autumn, a warm layer for after dark and something for your head during the day. For winter, everything you would take to a cold city plus a hat, because you will want it at four in the morning. For high summer, water in volume, shade for your head and the acceptance that the middle of the day is for sitting still.

What no month can settle. Whether the sky is clear on your night. The desert has overcast nights and nights with sand moving in the air, and the honest position is that nobody selling you this trip knows what yours will look like. What is knowable is that you will be behind the dunes, away from the road, with the camp around you — and that part is in the fare.

Timing and choice of listing are closer to the same decision than most people expect, because the thing the season changes most is how hard the driving days feel. Four situations cover almost everybody.

Spring or autumn, three days, keeping it simple. $137, our top pick, at 4.9 across 22,054 reviews. In a comfortable month the three-day shape is the right one: two driving days and the night in the sand, with nothing wasted. If you want the same shape for less, $63 is the floor of the site at 4.9 on 157 reviews.

High summer, when the days are the problem. $190 at 4.8 on 139 reviews, or $256 at 4.8 on 79. Four days and two nights means the long drives are cut in half and you are out of the vehicle during the hottest hours rather than in it.

Winter, when the night is the problem. A private tent is worth more in January than in April. $80 is the cheapest here with one, at 4.7 across 2,411 reviews, and $94 is the other, at 4.6 on 1,111.

Any season, if you are travelling north afterwards. $100, $102 and $145 end in Fes rather than bringing you back, which removes a whole day on the road — and a day less in a vehicle is worth most in the months when the vehicle is hot.