MADRID — Winds from the Sahara continued to send streams of sand drifting over the Canary Islands on Monday, creating chaos as the swirling sands forced planes to be grounded, disrupted traffic and exacerbated wildfires.

Ángel Víctor Torres, the regional president of the islands, a Spanish archipelago, told Spanish national television that it was the worst such storm to hit the islands in 40 years. He described its arrival as “a nightmare weekend.”

He said on Monday that the situation remained worrying on at least four islands, including Gran Canaria, which faces the greatest threat of wildfires.

The Spanish airport operator, Aena, reopened the archipelago’s airports on Monday, although it said that traffic would resume gradually and advised passengers to check with the airlines before heading to the airport. All of the islands’ airports were shut on Saturday because of strong winds and low visibility, leaving thousands of tourists stranded.