Broomfield Weather -- Broomfield County, CO

Broomfield, CO -- Plains City in Its Own County

Broomfield sits 83 feet higher than Louisville and roughly 1,000 feet lower than the foothills communities west of it -- a small gap that produces a measurably different day. Where Nederland is dealing with snow, Broomfield is often dealing with wind and bare ground. The city occupies the open plains along the US-36 corridor between Boulder and the Denver metro edge, and since November 2001 it has been its own city and county, carved out of four neighbors so that one municipality no longer straddled Boulder, Adams, Jefferson, and Weld.

That flat, unobstructed position is the whole story of Broomfield's weather. There is no terrain between the city and the Front Range to break a downslope wind, so Chinook and Bora events arrive at close to full strength and sustain longer here than in the sheltered pockets west of Boulder. Winter snow totals run lighter than anywhere in the foothills, and what does fall is frequently redistributed rather than accumulated -- drifting across open ground and stripping exposed south-facing slopes bare within a day.

Summer brings the plains pattern rather than the mountain one. Afternoon convection typically builds over the Divide and drifts east, arriving over Broomfield later and drier than it does over Nederland or Ward, and the city's open sky means hail and gust-front outflow are the storm hazards that matter more than rainfall totals. The Broomfield Open Space trail network and the US-36 bikeway are both fully exposed, which makes wind rather than temperature the variable worth checking before heading out.

Fire Risk and History

Broomfield carries a low wildfire risk relative to Boulder County's foothills communities -- there is no wildland-urban interface along its boundaries and no forested fuel load. That is not the same as no risk. The Marshall Fire of December 30, 2021 burned immediately northwest of here through Superior and Louisville, destroying 1,084 homes in a single afternoon on terrain that looks a great deal like Broomfield's: dry winter grassland under an extreme downslope wind event, with no forest involved at all.

The lesson the Marshall Fire wrote for the whole US-36 corridor is that plains grass under a 100-mph wind is a fuel, and December is not the off-season. Broomfield's exposure is the same fuel type in the same wind regime, on the far side of a boundary the fire never had to respect.

Elevation and Microclimate

At 5,420 feet Broomfield sits near the middle of the Front Range urban corridor's elevation band -- above Denver, below Boulder's foothills edge. UV exposure runs roughly 20 percent stronger than at sea level, and the thin, dry air produces a wide daily temperature swing: mornings can run 30 degrees cooler than afternoons in spring and fall. Summer highs average a degree or two warmer than central Boulder, and the growing season runs slightly longer than in the canyon towns to the west.

Flood Zone Information

Broomfield's developed areas are largely designated FEMA Flood Zone X, indicating minimal flood hazard. Big Dry Creek and its tributaries cross the city and carry the localized risk that does exist, and the September 2013 regional flood produced high flows along those corridors without the catastrophic residential damage seen upstream in the St. Vrain and Fourmile drainages. Parcel-specific designations change with map revisions and should be confirmed at the Flood Map Service Center.

Nearby Weather Pages

• Louisville weather -- adjacent US-36 corridor city, Marshall Fire impact zone
• Superior weather -- immediate northwest neighbor, Marshall Fire ground zero
• Lafayette weather -- plains city north on SH-7

References

• City and County of Broomfield
• Marshall Fire and Wind Event Recovery -- Boulder County
• FEMA Flood Map Service Center