A three-day-old wildfire erupted with catastrophic fury Tuesday, ripping across the foothills neighborhoods of Colorado Springs, devouring an untold number of homes and sending tens of thousands fleeing to safety in what was shaping up as one of the biggest disasters in state history. “This is a firestorm of epic proportions,” said Colorado Springs Fire Chief Richard Brown. The Waldo Canyon fire in El Paso County — which had been growing in the forested hills on the city’s west side — blew into an inferno late in the afternoon, raging over a ridge toward densely populated neighborhoods.

An apocalyptic plume of smoke covered Colorado’s second-largest city as thousands of people forced to evacuate clogged Interstate 25 at rush hour trying to get to their homes or to get out of the way.

By nightfall, roughly 32,000 people left their homes, chased out by the flames.

“We have homes burning right now,” El Paso County Sheriff Terry Maketa said shortly before 9 p.m.

The sheriff was among those forced from their homes by the fire.

“This is a very bad day,” said Colorado Springs Mayor Steve Bach.

As the fire continued to grow, all of northwest Colorado Springs was ordered evacuated, including the Air Force Academy.

“People are freaking out,” said Kathleen Tillman, who drove up I-25 from Pueblo to her house in northern Colorado Springs. “You are driving through smoke. It is completely pitch black, and there is tons of ash dropping on the road.”

At the same time the fire in Colorado Springs was erupting with a new fury, a lightning-sparked wildfire in Boulder blew up in the tinder-dry forest above the city. The Flagstaff fire grew in minutes to an estimated 228 acres and sent a smoke column over Boulder Valley. Twenty-six homes were evacuated, and residents of more than 2,000 homes in south Boulder were told to be ready to flee as the fire crept one ridge away from coming into the city.

Fire crews assembled at Fairview High School in case the wildfire burned into the city.

“This is the structure-protection plan,” said Jeff Long, battalion chief for Boulder Fire Rescue. “We are staying here in case it takes a turn for the worse. As long as the city is threatened, we’ll be here.”

It is a scenario that firefighting officials have feared as the conditions continued to get worse over the past week.

Scorching temperatures have baked the Front Range for several days as thousands of firefighters on the ground and more than 100 planes and helicopters have been battling more than eight wildfires across the state.

Denver tied a record with its fifth straight day of temperatures of at least 100 degrees, and weather in the 90s is expected to continue for several days even as officials hoped that seasonal subtropical moisture would eventually creep into the region and bring much-needed rain.

While Colorado Springs and Boulder took over the headlines, crews working on the High Park fire west of Fort Collins was measured at 87,250 acres with still 55 percent containment. That fire, the most destructive in state history, has torched at least 257 homes, nine more than previously thought.

Conditions are dry throughout the state. Even a fire near Last Chance on the Eastern Plains blew up to 45,000 acres in just eight hours.

But as darkness arrived, it was clear that the biggest fight in the state was in Colorado Springs, where ghostly orange flames rose across the city’s western edge.

Gov. John Hickenlooper arrived in Colorado Springs late Tuesday.

“The bottom line is we’re just going to have to work through this — all of us,” Hickenlooper said. “We just flew over the fires. … It was like looking at a military invasion.”

Wind gusts of 65 mph and the hottest day on record for Colorado Springs — the high hit 101 degrees — proved to be an explosive combination for the Waldo Canyon fire, which until Tuesday had not touched a structure.

“I’ve seen a lot of fires, but I have never seen one move this quickly,” Sheriff Maketa said.

By early evening, the website for the Flying W Ranch, a Western-themed attraction west of Garden of the Gods, announced that it had “burned to the ground.”

“Please keep us in your thoughts and those whose homes are close to us,” an official of the Flying W Ranch said in an e-mail.

Denver Post staff writers Kurtis Lee, Tom McGhee, Erin Udell and the Boulder Daily Camera contributed to this report.