The Sahara Desert is famously hot, dry, generally inhospitable and covered in sand as far as the eye can see. It’s a little bit more diverse than that in reality, however, with lush green segments dotted along the Nile Valley and scattered in the margins surrounding an extremely arid heart – and, yes, precipitation does fall across the region several times per year.
Snowfall on the sand dunes of the Sahara, however, is a little unexpected.
At the end of 2016, people were stunned to see a white duvet cover a notoriously arid part of the desert for the first time since 1979. Now, as reported by various outlets, it appears that it’s happened again. Some locales registered as much as 40.6 centimeters (16 inches) of glorious snow according to Forbes, although a precise weather report on this can't be found just yet.
In any case, it didn’t last long. After just a couple of hours max, the snow-covered sand reverted back to its original reddish tinge as temperatures rose again. According to Earther, only the tops of the nearby Atlas Mountains maintained their snowy hats for a little longer.
In all three slightly bizarre cases, the snow-riddled place du jour has been Ain Sefra, a northern Algerian town that’s commonly referred to as the Gateway to the Desert. It’s already about a kilometer or so above sea level, which means that snow is more likely here than other topographically lower parts of the desert – but snowfall like that observed this time around is decidedly unexpected.
It’s an area that is dominantly arid; it experiences fairly high average temperatures and not particularly stellar precipitation rates. This makes snow all the more improbable in this part of the world, so what the fresh hell is going on?
Temperatures can dip below the freezing point at this time of year, and that’s not actually that unusual, but that’s not all that’s required to generate a substantial amount of snow. You need a mass of water to be evaporated in the first place, or at least a lot of water vapor being delivered via atmospheric currents.
In this case, it appears a huge mass of cold air was dumped on the Sahara from North America, which made its way across the Atlantic over the past few days or so. Partly because of this, the local temperature hovered around 1°C (33.8°F) for a little while, creating the ideal conditions for a sudden snowfall.
It’s difficult to tell if this will be more common or far rarer in the future. The region snaps between periods of humidity and aridity faster than anyone can currently explain, although human agriculture has been thought to play a role in the latter.