The Cameron Peak fire northwest of Fort Collins blew up Saturday, prompting a new round of evacuations and reportedly making a run into Rocky Mountain National Park, which has closed the popular Trail Ridge Road.  

The fire, which ignited Aug. 13 in the Arapaho and Roosevelt National Forests, grew to 34,289 acres, up from roughly 26,000 acres. The blaze sent a plume roughly 40,000 feet into the air during continued burning on Sunday, the National Weather Service in Boulder reported. More than 800 firefighters are assigned to the blaze. Containment is estimated at 5%.

The erratic growth comes amid a heat wave affecting huge swaths of Colorado, including the Pikes Peak region, where a hazardous weather outlook warned of a “critical” potential for new fires.

Snow in the forecast for Colorado Springs 48 hours after hottest day of the year

Wind was especially a problem in areas where the Cameron Peak fire was burning, with gusts of up to 40 mph.

Hot, windy weather was to continue in Larimer County on Monday, though a change was in store for Monday night, offering cause for optimism with “drastically colder temperatures” and up to 6-12 inches of snow across the fire area, according to a fire information page on inciweb.org.  

The Fort Collins Coloradoan reported Sunday that continued growth pushed the fire into Rocky Mountain National Park. No estimate was given about the size of the intrusion. 

The National Park Service closed Trail Ridge Road at 3 p.m., citing the possibility of heavy smoke and poor visibility on the popular tourist draw, according to a news release. Old Fall River Road in Rocky Mountain National Park is also closed until further notice, along with several trails.

Cameron Peak fire officials upgraded voluntary evacuations to mandatory for some residents in the Pennock Pass area, warning of immediate and imminent danger. They asked people in the area to leave “as quickly as possible,” according to an emergency notice from the Larimer County Sheriff’s Office.

Colorado Wildfire Map

Saturday’s increase in size brought complaints from Fort Collins residents on social media sites about ash raining down in their neighborhoods. The Coloradoan said more reports of falling ash came Sunday from as far as Greeley and the Denver metropolitan area. 

The Cameron Peak fire is burning roughly 15 miles southeast of Red Feather Lakes, moving through heavy timber stands over rugged terrain. The cause of the blaze remains under investigation.