Thornton fire sends thick black smoke over Denver metro as evacuations ordered and I-25 shut down

A fast-moving Thornton fire pushed a towering plume of thick, black smoke over the north Denver metro area on Wednesday, Feb. 25, forcing neighborhood evacuations, disrupting school operations, and shutting down a key stretch of Interstate 25 during the early afternoon. The fire, burning in grasses and open land near major roads and businesses, spread in gusty, dry conditions that have elevated fire danger across the region.

Emergency crews worked to protect homes and commercial areas as smoke reduced visibility and drifted across travel corridors, triggering closures aimed at keeping drivers out of harm’s way and giving responders room to operate.

Thornton fire: evacuations ordered near neighborhoods, school, and businesses

Local police and fire crews moved quickly to clear people from areas northeast of the Thornton fire, including door-to-door notifications in nearby neighborhoods. A high school and several businesses near the 84th Avenue corridor were evacuated as the smoke column thickened and the fire behavior intensified.

Residents not at home were directed to report to a designated relocation site at a nearby water park facility and were advised not to return until officials lifted evacuation guidance. Emergency managers emphasized that evacuation zones can shift rapidly when wind gusts push flames and embers into new pockets of vegetation.

I-25 closures: traffic disruption grows as smoke crosses major corridors

The Thornton fire led to a major shutdown of I-25 in both directions as smoke and safety concerns increased. The closure began around the early afternoon and expanded as conditions evolved, impacting commuters and freight traffic moving through the north metro area.

Drivers were urged to avoid the corridor not only because of reduced visibility but also because fire apparatus, law enforcement vehicles, and ambulances needed clear access to perimeter roads. Alternate routes quickly backed up as traffic diverted away from the interstate.

Weather and fire danger: winds and low humidity amplify risk

Wednesday’s conditions created a high-risk setup: strong winds, unseasonably warm temperatures, and extremely low humidity. That combination increases the chance that grass fires will run quickly, jump breaks, and generate spot fires downwind.

A red flag warning covered the lower-elevation Front Range and nearby plains through the late afternoon and early evening. In these conditions, even a small ignition can turn into a rapid response event, and smoke impacts can spread far beyond the burn area.

Thornton fire investigation: cause not confirmed as crews prioritize containment

The cause of the Thornton fire remained under investigation Wednesday afternoon. Fire crews prioritized containment lines, structure protection, and keeping the incident from extending into denser residential pockets.

Officials signaled that more details would follow once conditions stabilized and investigators could safely access the origin area. In many fast-moving grass fires, determining a cause can take time because wind and suppression activity can disturb initial evidence.

What residents should know: closures, re-entry, and smoke precautions

While evacuations and closures are active, residents are being asked to follow official instructions closely and avoid “drive-by viewing,” which can slow emergency vehicles and create new hazards. Smoke can also affect people well outside the evacuation footprint, especially those with asthma or other respiratory conditions.

A practical approach for the rest of the day includes limiting outdoor exertion, keeping windows closed if smoke drifts into neighborhoods, and checking for updates on evacuation boundaries before attempting to return home.

The Thornton fire remains a fluid situation, shaped by wind shifts and rapidly changing visibility on major roads. For residents and travelers, the key near-term watch points are when evacuation zones are reduced, when I-25 reopens, and whether wind gusts ease enough to allow crews to gain durable control of the fire’s edge.