SALT LAKE CITY — A "rare" thunderstorm with heavy winds gusting up to 76 mph left 12,000 homes without electricity most of Sunday evening and a few thousand throughout the night as crews worked to restore power and reopen major highways by this morning.

By 10 p.m., only 8,000 homes were still without power and officials expected another 2,000 to have power restored by 11 p.m. All but 1,300 homes in Farmington were to have power by shortly after midnight and all of the city's residents were expected to have power back on by this morning.

Legacy Highway, which was closed around 4 p.m. after downed power lines closed off access, was expected to be open in both directions by 4 a.m. today, "just in time for the morning commute," Utah Highway Patrol Sgt. Greg Lundell said.

Dozens of small tree and field fires sparked by the downed power lines kept fire crews hard at work and the strong gusts of wind prompted the National Weather Service to issue a strong wind advisory until 8 p.m.

Forecasters called the gusts of wind mixed in with thunderstorms a "significant" storm given that such strong wind gusts are more common in the flat plains of central Utah but rare in large metro areas.

"We don't usually see wind gusts above 70 miles per hour around here," National Weather Service meteorologist Steve Rogowski said. "It's a stronger cold front with temperatures dropping significantly."

Gusts ranging up to 76 mph that hit Centerville and Salt Lake around 3 p.m. caused serious damage at the Salt Lake International Airport and required about 10 flights into Salt Lake to be diverted. Airport officials said the diverted planes returned to Salt Lake by 9 p.m. and the airport was back on schedule.

The airport also saw serious damage to its general aviation hangar along with a number of flight delays. Debris from the damaged hangar closed an adjacent road, and the passenger-side window of an airport operations pickup truck was blown out, Rogowski said.

Cities outside of Salt Lake recorded gusts up to 50 and 60 mph. Bountiful gusts reached 64 mph and parts of Ogden were hit by 61 mph gusts.

Forecasters said the cold front was already moving into central Utah by Sunday evening but would leave the Salt Lake Valley with cooler temperatures — low 80s — until Wednesday. By Thursday, the temperatures are expected to be back in the low to mid-90s, and higher humidity is expected to hit the Salt Lake Valley again.

The high winds also shut down parts of I-80 and Legacy Parkway.

Officials were forced to shut down eastbound traffic on I-80 at 5600 West when power lines collapsed onto travel lanes. Westbound traffic was also diverted at Wright Brothers Drive, and travelers were advised to take state Route 201 as an alternate. Both lanes were expected to be reopened by midnight.

The Salt Lake Valley had a total of 5,000 homes without power Sunday with a majority of that in West Valley and parts of Salt Lake.

Officials also reported 1,500 homes in Riverdale and another 3,000 in Ogden were without power. Riverdale residents had power restored by 7 p.m. and all but 400 Ogden residents had power back by 10 p.m.

Another 2,400 Eden homes that lost power about 5:45 p.m. had power restored by 9:30 p.m.

Crews were spread thin as they worked to restore power in the numerous outage areas and UHP officials called in extra troopers to help with the road closures.

"It's unusual to have lines come down this much," Lundell said. "And there's not much we can do until Rocky Mountain Power can get the manpower out there."

National Weather Service forecasters in Salt Lake City issued the wind advisory in response to heavy gusts that started around 3 p.m.

Rocky Mountain Power officials said they managed to restore power to 5,000 customers but still had 12,000 without power at 8 p.m.

"This is a little unusual," Rocky Mountain Power spokesman Dave Eskelsen said. "This is a pretty big thunderstorm. We've had both lines down and pole damage."