Marshall Fire (2021)
Boulder County (Louisville, Superior), Colorado · Dec 30, 2021 – Dec 31, 2021
Most destructive wildfire in Colorado historyAcres burned
6,026
Lives lost
2
Structures destroyed
1,084
Year
2021
Estimated damage
~$2 billion in insured losses
Duration
Catastrophic damage in a single afternoon; snow helped contain it next day
Evacuations
~37,000 people evacuated on short notice
What happened
The Marshall Fire is the most destructive wildfire in Colorado history. Driven by 100+ mph winds across grasslands on December 30, 2021, it tore through suburban Boulder County neighborhoods, destroying more than 1,000 homes in a single afternoon — in winter.
Cause
Investigated; multiple ignition sources
Location
Boulder County (Louisville, Superior), Colorado
Key facts
- ▪Most destructive wildfire in Colorado history
- ▪Burned in late December — a grass-driven winter fire
- ▪100+ mph downslope winds
- ▪Destroyed 1,084 homes in suburban neighborhoods
Replay the Marshall Fire in the spread simulator
This centers the wildfire-spread simulator on the Marshall Fire’s documented ignition point and replays its conditions on 2021-12-30 — the day’s strongest wind, temperature, and humidity from the open-meteo historical archive (which set the fire-day fuel moisture) — run through the same Rothermel surface-fire model used across FireRisk. Press ▶ Simulate to watch how fire tends to move under those conditions.
⚠️ Educational reconstruction — not the real fire perimeter
This is a simplified model of how fire spreads under the 2021 conditions, not the Marshall Fire’s actual burned area, official progression, or a prediction of any current fire. It cannot account for real fuels, suppression, spotting, or how conditions changed hour to hour. For real-time fire information always follow Watch Duty, official agencies, and local authorities — and call 911 in an emergency.
Loading the 2021 fire-day conditions…
Reminder: an educational reconstruction of fire spread under the 2021 conditions — not the Marshall Fire’s actual perimeter, an official record, or a forecast. Modeled spread, direction, and timing are illustrative only. Never rely on it for any safety decision.
Aftermath & what changed
The Marshall Fire shattered the assumption that wildfire is a forest/summer problem — a grass-fueled suburban fire in winter. It drove Colorado to launch a state FAIR Plan and sharpened scrutiny of WUI building codes and underinsurance.
Could your home survive a fire like the Marshall Fire?
Check your address for a 0–100 wildfire risk score, every fire recorded nearby, and the hardening steps that change the outcome.
Related major fires
Marshall Fire FAQ
When was the Marshall Fire and where did it burn?
The Marshall Fire started Dec 30, 2021 in Boulder County (Louisville, Superior), Colorado, and was contained Dec 31, 2021.
How many acres did the Marshall Fire burn?
The Marshall Fire burned approximately 6,026 acres.
How many people died in the Marshall Fire?
Approximately 2 people died in the Marshall Fire.
What caused the Marshall Fire?
Investigated; multiple ignition sources.
Figures are approximate and compiled from official agency reporting; totals for recent fires may still be revised. FireRisk.ai is an independent wildfire-risk service.