The Cameron Peak wildfire in northern Colorado is officially the largest ever observed in the Centennial State, with strong winds pushing the blaze — still just 56 percent contained — ominously close to Fort Collins. “Extreme fire activity” on Wednesday prompted numerous evacuations, with officials citing an “immediate and imminent danger.”

Expanding more than 30,000 acres between late Tuesday and early Thursday, the Cameron Peak Fire, which began Aug. 13, has now charred 164,140 acres. Roaring westerly winds, up to 70 mph, helped it make a single-day eastward run greater than 15 miles.

It’s the largest growth of the wildfire since Sept. 6 and 7, when record hot and dry conditions in northern Colorado allowed it to triple in size and swell 66,426 acres in two days. That’s when the fire first hit the 100,000-acre mark.

The blaze, which has consumed an area bigger than Chicago, grew by an area half as large as Washington in a single day Wednesday.

Now it has claimed top spot for the largest wildfire in Colorado history, beating out the Pine Gulch Fire, which also set a record this year, charring more than 139,000 acres. That fire affected northwest Colorado north of Grand Junction after being ignited by a lightning strike July 31 and continued to spread until mid-September.

Evacuations west of Fort Collins

Mandatory evacuations have been issued for much of the Arapaho and Roosevelt National Forests, and were extended Wednesday for Lory State Park. Rist Canyon and Stratton Park, northeast of Mount Ethel and Buckhorn Mountain in the high terrain northwest of Fort Collins, were also placed under mandatory evacuation.

In addition, the Larimer County Sheriff’s Office has implemented mandatory evacuations in areas downwind of the fire in areas like Horsetooth Mountain, which overlooks Fort Collins.

“All residents and business occupants should evacuate the area immediately and as quickly as possible,” wrote the Sheriff’s Office. “Do not delay leaving to gather belongings or make efforts to protect your home or business.”

The eastern limb of the fire is about 13 or 14 miles west of Fort Collins, its footprint inching eastward with each successive update. But Fort Collins appears for now to be relatively safe. The Horsetooth Reservoir fills a six-mile strip between the fire and Fort Collins. The city is also at a considerably lower elevation than the mountains in which the fire is burning; fires travel downhill much more slowly than uphill.

That’s not to say new spot fires aren’t possible, especially when strong westerly winds lift and carry embers.

Hazardous air quality

Strong wind gusts on Wednesday pushed billowing plumes of smoke overhead of Fort Collins, transforming day into night beneath the eerily dark shroud. Just to the south, crystal-clear blue skies shone.

The smoke brought about degraded air quality in Fort Collins, with dangerous ground-level concentrations of particulate matter and pollutants. An air-quality alert was in effect Thursday.

“If visibility is less than 5 miles in smoke in your neighborhood, smoke has reached levels that are unhealthy,” wrote the Colorado Department of Public Health and Environment.

Burn bans

All outdoor burning is prohibited in Rocky Mountain National Park, a ban officials plan to leave in effect “until further notice.”

Part of the region being lapped at by flames has been hard hit in recent years by beetles, also a rampant problem in California. They kill the trees, leaving dead, parched trunks standing. That dry, unfelled timber sits ready to burn. It’s been doing so in Colorado for weeks.

“The Cameron Peak Fire moved into Rocky Mountain National Park on Saturday, September 6... in steep thick beetle killed forests with significant standing dead trees as well as dead and down fuel,” wrote the National Park Service.

On Wednesday, National Weather Service Doppler radar indicated the Cameron Peak Fire’s smoke plume had towered to more than 16,000 feet high. Radar data suggested small-scale eddies and firewhirls were possible within fire.

Poudre Valley REA, an electric co-op serving Larimer, Weld and Boulder counties, cut power to Buckskin Heights, Redstone Canyon and Cedar Park on Wednesday at the request of Incident Command. Estes Park Power and Communications did the same in Glen Haven and along County Road 43.

Glen Haven is about six miles northeast of Estes Park and just under 20 miles west-northwest of Loveland. The unincorporated community is home to a little more than 100 people.

Improving weather

Fire weather will improve in the days ahead, making it a bit less difficult for fire crews to combat the flames. Helping them have been overnight temperatures in the 30s that allow the air to moisten after dark.

On Thursday night, upper 20s are likely. Rain and snow showers will also enter the forecast late in the weekend into early next week, with the precipitation welcome over the parched landscape.

Progressively warmer and drier weather looks to return toward the middle of next week.

Increased extreme fire behavior and the area burned by wildfires have been linked to climate change, since warming temperatures help to dry out vegetation and make it easier to burn. The intensity of “heat domes,” or ridges of hot high pressure that can bring about fire weather, has also grown in much of the West.

The entirety of Colorado is suffering from drought conditions, according to the federal government’s U.S. Drought Monitor. About 97 percent of the state is in “severe drought” or worse, including the Cameron Peak Fire area.

All 10 of Colorado’s largest fires on record have occurred since 2002, with the top two occurring in the last three months.

Jason Samenow contributed to this report.