Marshall Weather -- Boulder County, CO

Marshall, CO -- Wind Gap Community at the Base of Marshall Mesa

At roughly 11:00 a.m. on December 30, 2021, a grass fire started near the intersection of Colorado 93 and Eldorado Springs Drive, and within hours it had become the most destructive wildfire in Colorado history by structures lost. The Marshall Fire burned more than 6,000 acres and destroyed over 1,000 homes across Louisville, Superior, and unincorporated Boulder County. It takes its name from this place.

Marshall is not a town. It is a small unincorporated community in Boulder County at the foot of Marshall Mesa, a remnant of the coal-mining settlements that worked the seams beneath this stretch of the Front Range foothills. At about 5,500 feet, it occupies the gap where the mesa's south flank meets the open grassland running east toward Superior -- a topographic funnel that concentrates westerly downslope wind and accelerates it onto the plains.

That funnel is why the weather here is not the weather two miles in any direction. Winds recorded during the December 2021 event gusted well past 100 mph through this corridor, and while that was an extreme, sustained winter windstorms are the defining local pattern rather than an anomaly. The mesa trail network and the Community Ditch corridor are fully exposed to it. Snow rarely persists on the wind-scoured south-facing slopes, which is precisely what leaves cured grass available as fuel in the middle of winter.

Fire Risk and History

Marshall carries an extreme wildfire risk, and it is the location that demonstrated why grassland fire risk on the Front Range is a year-round condition rather than a summer one. Investigators concluded the December 2021 event had two separate ignitions -- one from week-old embers on private property, and one from hot particles discharged by an Xcel Energy power line near the Marshall Mesa trailhead. Neither required a forest.

What made it catastrophic was the combination this location specializes in: cured winter grass, no snowpack, and a downslope wind event funneling through the mesa gap at highway speed. The Boulder County Community Wildfire Protection Plan treats the grassland-interface communities along this corridor as a distinct hazard class from the forested canyons to the northwest, and the mitigation guidance differs accordingly.

Elevation and Microclimate

At 5,500 feet, Marshall sits above Louisville and Superior to its east and below the foothills communities climbing west toward Eldorado Canyon. The mesa immediately south blocks low-angle winter sun on parts of the area while doing nothing to slow west wind, producing a microclimate that is simultaneously colder in shadow and drier in exposure than the open plains a few miles away. UV runs about 20 percent stronger than at sea level.

Flood Zone Information

The Marshall area is largely designated FEMA Flood Zone X, reflecting minimal flood hazard on this bench above the creek corridors. Community Ditch and the small drainages off Marshall Mesa carry the localized risk. The September 2013 regional flood concentrated its damage in the canyon-mouth towns north of here -- Lyons, Jamestown -- rather than on this grassland bench, though parcel-level designations should be confirmed at the Flood Map Service Center.

Nearby Weather Pages

• Superior weather -- immediately east, took the fire's first urban impact
• Louisville weather -- next city east, roughly 550 homes lost
• Eldorado Springs weather -- canyon mouth southwest, same wind corridor

References

• Marshall Fire and Wind Event Recovery -- Boulder County
• 2024 Boulder County Community Wildfire Protection Plan
• FEMA Flood Map Service Center