The skies first became tinged a dusty tan across Spain’s Canary Islands on Saturday. By Sunday, an eerie-brown daylight dawned over an archipelago socked in by sand, prompting the closing of airports and even schools by Monday.

The culprit in this sand invasion is a large storm spinning over the northeastern Atlantic Ocean. The counterclockwise air circulation around the low-pressure area over the northeast Atlantic has drawn in sand from the Sahara Desert, propelling the dust directly over the Canary Islands before transporting it westward, toward the center of the storm. The Spanish autonomous territory of more than 2 million was the first stop for the Sahara dust, and it’s the area most heavily affected.

On Gran Canaria, the island’s landscape disappeared behind salmon-colored curtains of dust over the weekend, trees whipping in the strong winds that pelted dust against window frames and even into homes.

On La Palma, the chain’s far northwestern island, the air quality index at one point Monday afternoon stood at more than 800 because of the presence of gritty fine particulates and aerosols in the air. According to the U.S. Environmental Protection Agency, values under 50 are “good,” while anything over 100 is “unhealthy.” Once the air quality index reaches 300, it’s considered “hazardous.”

Between 1 p.m. and 3 p.m. Saturday, the visibility at Gran Canaria Airport dropped from more than five miles to less than a mile. By 5:30 p.m., it was impossible to see more than a quarter mile away; the sun was blotted out by the dense haze.

Satellite imagery captured these jets of dust rushing toward the Canaries, with roll clouds forming along the leading edge of their choking breeze.

While the territory’s airports were no longer closed to aviation traffic Monday, remnant delays and cancellations lingered into the start of the workweek. Schools were closed as well.

It’s not just the storm to the west that caused this dust event. It’s actually a combination of weather features. A clockwise-spinning high-pressure system has sat to the west of the Iberian Peninsula. Like two interlocking gears, the systems are channeling a strip of air westward in between, creating an atmospheric conveyor belt of sorts that’s draping an opaque shroud over the Canaries.

That same high-pressure system also extends into southern Europe and has been contributing to record high temperatures in France.

As of Monday, a tendril of dust had snaked its way more than a thousand miles from its source, swirling into the low-pressure system as if orbiting the drain of an enormous atmospheric sink.

By midweek, the air should clear markedly over the Canaries as high pressure begins to nudge in from the north.

However, a thin veil of dust may pass over the Azores by late in the week and may be near the United Kingdom as the weekend nears — albeit in significantly reduced concentrations. Instead of shutting down airports, the dust may bring about only a more vibrant sunset or sunrise or add a subtle, milky haze to the air.

A similar setup in April brought muddy rain to the U.K., while carrying dust as far north as Scandinavia and the Arctic Circle.