< 12px;">Smoke from three major California wildfires drifted into the Las Vegas Valley, blanketing the region in a haze of unhealthy air Wednesday.
< 12px;">

< 12px;">As the fires, which were burning in Southern Cali- fornia’s mountains east of Los Angeles, sent smoke to Southern Nevada, residents noticed they had seen ash falling from the sky while monitoring sites from Jean to Mesquite showed unhealthy air during most of the daylight hours, officials said.
< 12px;">

< 12px;">By 6 p.m. Wednesday, the situation seemed to get better, however.

< 12px;"> Clark County < 12px;">monitoring stations showed improved air conditions with most stations west of Interstate 15 in the moderate range with a handful on the east side rated as unhealthy for sensitive groups. Green Valley and Boulder City remained in the unhealthy category.

< 12px;">< 12px;"> “Smoke will still hang over parts of southern Nevada though which will result in hazy skies at times tonight into Thursday morning,” the National Weather Service’s Las Vegas forecast office said in a forecast discussion posted online Wednesday night.

< 12px;">< 12px;">But a cold front approaching the valley overnight should push the air in a different direction, forecasters said.

< 12px;">< 12px;">“This will probably last all day, into the evening and tonight,” National Weather Service meteorologist Brian Planz said of the smoke on Wednesday. “A wind shift to the northwest tomorrow should improve things”

< 12px;">< 12px;">Weather cameras were showing gray skies clearing as the evening started.

< 12px;">< 12px;">The three fires — the Bridge Fire, the Line Fire and the Airport fire — torched dozens of homes and forced thousands of people to evacuate, officials said.

< 12px;">< 12px;">At least a dozen people, mainly firefighters, were treated for injuries that were mostly heat-related, authorities said. One person from Orange County was burned. No deaths had been reported.

< 12px;">< 12px;">The wildfires have been endangering tens of thousands of homes and other structures across the region after they sprung to life during a triple-digit heat wave over the weekend. Other major fires were burning in Idaho and Oregon.

< 12px;">< 12px;">As well, the Davis Fire south of Reno had forced about 20,000 people to flee.

< 12px;">< 12px;">In the tight-knit community of Wrightwood that sits on the Pacific Crest Trail, authorities implored residents to evacuate the exploding Bridge Fire, which burned more than a dozen homes in the area.

< 12px;">< 12px;">Resident Erin Arias said she was racing up the mountain when she got the sudden order to leave and did, grabbing her passport and dog. On Wednesday, she and her husband doused water on the roof of their still-standing home. Their cat was missing, she said.

< 12px;">< 12px;">“It’s absolutely scary,” Arias said, looking at the burned embers of her neighbor’s home. “We’re really lucky.”

< 12px;">< 12px;">At Harry Reid International Airport, the flight tracking website Flight-Aware said about 483 flights had been delayed Wednesday, including 262 delays from Southwest alone.

The Clark County Division of Air Quality also issued a smoke alert for Wednesday.

The Associated Press contributed to this report.