Authorities shut down Interstate 15 in both directions along the California–Nevada border as a “major dust storm” pummeled the freeway for hours on Sunday, snarling traffic and delaying flights.

Wind speeds soared up to 40 to 50 mph with occasional gusts reaching even higher, resulting in some downed trees, said Dan Berc, a meteorologist with the National Weather Service’s Las Vegas office. The Harry Reid International Airport was experiencing an average delay of 165 minutes for departing flights, and 769 flights were delayed as of Sunday evening, per Federal Aviation Administration data reported by KLAS.

The closure between Nipton Road, California, and Primm, Nevada, ended by 5 p.m. as the gusts subsided, but similar conditions are expected to persist Monday as a wind advisory remains in effect through 6 p.m., the weather service said. 

“The winds today are already just starting to go down,” Berc said. “We’re not going to see winds quite as strong as yesterday, but they’ll be slowly decreasing throughout the day and should be calm by this evening.”

After a strong low-pressure system brought record-breaking rainfall to California last week and continued to move eastward, a cold front came through behind it, producing the strong northerly winds, he explained. 

“We could still see some localized areas of blowing dust across the road,” he said. “If you encounter it, keep both hands on the wheel, pull over and wait for visibility to improve.”