Until Saturday, Utah’s 2021 fire season had not quite lived up to the dire predictions officials offered back in May when they warned Utah could see its worst fire season on record. While West Coast states have seen apocalyptic fire, Utah so far enjoyed relatively calm in the face of record heat and historic drought.

That calm went up in smoke Saturday when a car dragging a bad catalytic converter ignited a fire that quickly threatened Summit County neighborhoods, triggering evacuations and a massive firefighting response.

As of last Wednesday, only about 60,000 acres had burned this season, according to the Utah Division of Forestry, Fire and State Lands. Flames have overrun that much acreage in a single day in California, putting up enough spoke in recent weeks to ruin Salt Lake City’s air quality 500 miles away.

On Sunday, however, Salt Lakers were gagging on smoke from their own backyard.

This weekend’s wildfire is a stark reminder of just how vulnerable numerous Utah communities are along the populated Wasatch Front and Back. This week, Summit Park is in the crosshairs, but it could just as easily be Emigration Canyon, Pinecrest, Pinebrook, Toll Canyon, Sundance, Porter Fork, Deer Valley, Ogden Canyon, Alpine or any other other community where homes have been built in wooded landscapes.

Some of these at-risk communities occupy narrow canyons served by dead-end roads, such as Lambs Canyon, which was evacuated not long after the fire broke out Saturday afternoon.

Utah’s changing climate, becoming undeniably warmer and drier over the past two decades, has made the situation more dangerous. Ironically, however, the drought may have worked in Utah’s favor, according to Sierra Hellstrom of the Northern Utah Interagency Fire Center.

“When you are in drought conditions like we have been over the winter, the vegetation doesn’t tend to get as high. We don’t see as much vegetative growth,” she said. “We actually have had quite a few fires, but because the vegetation wasn’t as thick, we’ve been able to catch most of them on initial attack and have been able to slow them down. We’ve had one in East Canyon, we had one in Art Nord, we had a couple along [Interstates] 80 and 84. But they’ve been able to catch them fairly quickly.”

This year, officials imposed fire restrictions early and often on Utah’s public lands and banned fireworks and target shooting in many places. Those effort clearly bore fruit, with human-caused fires way down compared with last year’s epidemic of fires resulting from carelessness.

“Restrictions were very broad, very early on. We need to limit [camp]fires just knowing that the vegetation was dry and the fuel moistures were low,” Hellstrom said. “That was a really big help. And people have been, for the most part, abiding by those [restrictions]. That seemed to be fairly successful.”

Early this summer an illegal campfire did start the Pack Creek fire that destroyed some homes near Moab, but the fire season has been a yawner since.

So what happened Saturday?

Sparks flying off a car traveling east through Parleys Canyon got into the dried grass beside Interstate 80. In a flash, four separate fires were burning. The fine, sparse fuels — such as dried grasses or other flammable material — along the road carried the flames into dried timber, and in minutes the fire was out control.

“It was just very receptive to fire. It was a hot, windy day,” Hellstrom said, with “all the conditions conducive to having a fire get fairly large.”

At only 619 acres on Sunday, Parleys Canyon Fire could still be contained before it does much damage. Or it might easily become the most destructive fire in Utah history in terms of property damage. They outcome may largely depend on weather.

The National Weather Service forecasted more hot, dry, breezy conditions through Monday, but predicted a welcome change as soon as Tuesday: the arrival of a cold front bringing some rain.

The genesis of the Parleys blaze is completely different from the last major fire that threatened mountainside communities. The Pole Creek and Bald Mountain fires of 2018 started with late-August lightning strikes high in wilderness areas on Mount Nebo. Because these fires were difficult to reach and did not appear to threaten anything, the U.S. Forest Service did not attack them aggressively at first. They burned with little spread for several days before a wind event whipped them into a conflagration that raced toward the Utah County subdivisions of Elk Ridge and Woodland Hills.

Firefighters and retardant drops kept flames out of neighborhoods and no homes were lost. However, subsequent debris flows damaged some rural properties, prompting several claims against the Forest Service, accusing officials of negligently allowing the fires to get out of control.

On the Parleys Canyon Fire, by contrast, little time was wasted mobilizing an all-out attack.

The fire itself was easy to reach and was clearly a threat the moment flames appeared just east of the mouth of Lambs Canyon, where nearly 100 seasonal homes are nestled into the woods several miles up a winding paved road.

No less than 15 aircraft were deployed Saturday, including two so-called “very large” airtankers and four others of the merely “large” variety. Running sorties out of the Salt Lake City, Park City and Ogden airports, the tankers delivered thousands of tons of chemical fire retardant in hopes of slowing the fire’s rapid spread up canyon toward Summit Park.

“We are fortunate here in northern Utah that the aircraft is located close by,” Hellstrom said. The Forest Service maintains a hangar for big tankers in Ogden.

The fire did stop spreading late Saturday, but that could have been the result of cooler temperatures and calmer winds that arrived at nightfall. Still, the aerial resources brought to bear during what remained of Saturday’s daylight hours were impressive and likely helped slow the fire’s march toward Summit Park.

Large airtankers carry between 2,000 to 4,000 gallons of retardant, which comes in a brightly colored slurry, and very large tankers carry more than 8,000 gallons. Hellstrom did not know how many drops these tankers made Saturday, but witnesses say there was a constant bombardment into the evening.

Retardant drops were credited with saving mountain subdivisions on Kane County’s Cedar Mountain in the 2012 Shingle fire, which had been sparked by an ATV riding in an area closed to motorized use in the Dixie National Forest.

Utah’s most destructive fire for property loss was probably the 69,000-acre Dollar Ridge fire in Duchesne County in July 2018, when flames destroyed 80 mostly seasonal homes scattered around a rural subdivision south of U.S. Highway 40. That fire was human-caused, officials said, but what exactly triggered it has yet to be disclosed.

If flames invade Summit Park, a mountaintop subdivision with hundreds of homes on the Park City of the Wasatch divide, the Parleys fire could blow Dollar Ridge away — even without burning nearly as much acreage.