Thornton Fire forces evacuations near 84th Avenue and Huron as I-25 shuts down under thick black smoke

A fast-moving Thornton Fire sent a towering column of thick, black smoke across the north Denver metro area on Wednesday, Feb. 25, prompting door-to-door evacuations near 84th Avenue and Huron Street and forcing a major shutdown of Interstate 25 as visibility deteriorated. The grass-driven blaze flared during high fire-danger conditions, with gusty winds and very low humidity helping flames run quickly across open ground and push smoke into heavily traveled corridors.

Officials urged people in nearby neighborhoods and commercial areas to leave early if they felt unsafe, warning that conditions could change quickly as wind shifts moved the smoke plume and fire edge.

Thornton Fire ignites near I-25 corridor and quickly escalates

Initial reports placed the start of the Thornton Fire around midday local time, roughly 2:00 p.m. ET, in a grassy area near the 84th Avenue corridor. Within a short period, the smoke column grew dense enough to be seen across the metro region, and responders began prioritizing life safety: clearing homes and businesses closest to the fire, creating access lanes for engines, and keeping traffic away from the heaviest smoke.

The fire’s behavior reflected a classic Front Range grass-fire pattern—rapid forward spread, frequent flare-ups as winds pulse, and spotty ignition in patches of dry vegetation. Even when flames remain relatively low, grass fires can race faster than people expect, especially when wind funnels along open spaces and roadway edges.

Evacuations expand around neighborhoods, businesses, and a high school

As the smoke thickened, law enforcement and firefighters began door-to-door notifications in neighborhoods northeast of the fire, while also clearing nearby commercial properties along 84th Avenue. A local high school in the area was evacuated and moved into controlled release procedures to reunite students with families away from the immediate smoke and traffic congestion.

Evacuation guidance focused on two practical dangers: the potential for flames to shift direction with wind changes, and the immediate health and visibility impacts of heavy smoke. Officials emphasized that people should not delay departure to gather belongings and should avoid driving toward the scene.

I-25 closures and gridlock: why the interstate was shut down

The Thornton Fire created one of the most disruptive transportation impacts seen in the metro area this month. I-25 was closed in both directions in the Thornton area as a precaution because smoke drifted directly over the roadway, reducing visibility and creating hazardous conditions for drivers.

The closure also provided responders a safer operating environment. With engines, law enforcement units, and medical support moving along frontage roads and ramps, keeping the interstate clear helped prevent secondary crashes and allowed faster repositioning if the fire jumped containment lines.

Drivers were urged to avoid the corridor entirely and expect heavy delays on alternate routes as traffic rerouted through local streets.

Weather conditions: wind, low humidity, and dry fuels drive rapid spread

Wednesday’s conditions were a major factor in the fire’s speed. Very low humidity, warm temperatures, and gusty winds combined to dry out fine fuels like grasses and weeds—exactly the fuel type that ignites easily and spreads fast.

In this setup, sparks from vehicles, equipment, or downed lines can trigger a fire that outruns suppression efforts in the first minutes. Even when crews establish a line, shifting wind can push smoke and embers across roads or into new pockets of grass. That is why officials repeatedly warned residents that evacuation zones and road closures could expand with little notice.

What to know right now: safety, smoke, and re-entry

For residents near the Thornton Fire, the main instructions are straightforward: follow official evacuation orders, avoid the area, and do not return until authorities lift restrictions. For those farther away, smoke can still pose a health issue—especially for children, older adults, and anyone with asthma or heart or lung conditions.

Here’s a quick status snapshot (all times ET):

As crews work to tighten containment, officials will likely prioritize reopening key roads once visibility improves and the fire edge is no longer threatening the interstate. The next public updates are expected to focus on whether evacuation zones can be reduced, when I-25 can safely reopen, and whether investigators can begin confirming a cause once the fire’s origin area is secure.