Lyons Weather -- Boulder County, CO

Lyons, CO -- St Vrain Canyon Gateway in Boulder County

Lyons sits at the confluence of the North and South St Vrain Creeks at the mouth of St Vrain Canyon, where the foothills meet the plains at 5,374 feet. The town is the eastern gateway to Roosevelt National Forest and the St Vrain corridor that leads northwest toward Estes Park and Rocky Mountain National Park. Red Rocks Open Space immediately north of town exposes the Dakota hogback geology that gives Lyons its characteristic red sandstone backdrop — the same formation that creates an amphitheater-like landform channeling wind from the canyon mouth across the community.

The canyon-mouth position gives Lyons a distinct microclimate relative to its plains neighbors. Down-canyon wind events are funneled and accelerated through St Vrain Canyon, producing sustained gusts in Lyons that regularly exceed speeds measured at nearby plains stations during Chinook and downslope episodes. Summer temperatures are moderated by afternoon upslope flows pulling cool air from the mountains, while winter downslope events can drive rapid warming from below freezing to well above. Lyons sits at the edge of the foothills precipitation shadow — drier than the mountains upstream but receiving meaningfully more snowfall and convective rainfall than the plains communities to the east.

Lyons bears the most direct legacy of the September 2013 Front Range flood of any community in Boulder County. Both the North and South St Vrain Creeks rose to record levels simultaneously, and the entire town was evacuated for weeks. Both road entrances to town were cut off by washed-out infrastructure, the water treatment plant was destroyed, and creek-adjacent residential areas sustained structural losses across multiple blocks. The town has since rebuilt with upgraded flood infrastructure and amended floodplain regulations, but the event remains the defining reference point for emergency preparedness and land-use decisions in Lyons.

Fire Risk and History

Lyons carries a high wildfire risk due to its foothills position at the wildland-urban interface along St Vrain Canyon. The surrounding terrain — dry ponderosa-grassland on the canyon walls, Red Rocks Open Space to the north, and dense riparian vegetation along the creeks — creates a fire environment that can escalate rapidly under Chinook or Bora wind conditions. The Cameron Peak Fire (2020) burned 208,913 acres in the watershed upstream and produced air quality emergencies in Lyons and downwind communities for weeks. The Fourmile Canyon Fire (2010) burned south of Lyons along the foothills corridor. Lyons has an active wildfire mitigation program; details at townoflyons.com.

Elevation and Microclimate

At 5,374 feet, Lyons receives approximately 20 percent stronger UV exposure than sea level. The canyon-mouth position produces significant diurnal temperature swings: warm afternoon downcanyon flows in summer, sharp overnight cooling as cold air drains from the mountains. Annual snowfall is higher than plains communities — typically 60–70 inches — but lower than higher-elevation foothills towns. The St Vrain Canyon corridor amplifies wind events that register as moderate at Longmont into gusts that regularly exceed advisory thresholds at the canyon mouth, particularly during November through March downslope events.

Flood Zone Information

Lyons is a FEMA Flood Zone AE community with significant flood hazard along both the North and South St Vrain Creeks and their confluence through town. The September 2013 flood set the modern benchmark — flows far exceeded the mapped 100-year levels, resulting in full town evacuation and years of infrastructure reconstruction. Many downtown and creek-adjacent parcels carry mandatory flood insurance requirements. Verify your parcel's specific designation at FEMA's Flood Map Service Center. The South St Vrain Creek at Lyons (USGS gauge 06724000) provides real-time streamflow data for this corridor.

Nearby Weather Pages

• Longmont weather -- plains city 12 miles east
• Hygiene weather -- small CDP between Lyons and Longmont
• Boulder zip 80302 weather -- south via US-36 canyon corridor