Foothill Shrublands

Precipitation to date in September was 0.3 inches at Ralston Reservoir, 0.6 inches below the normal of 0.86 inches; August 2026 ranked as the 53rd driest August on record for Jefferson County since 1895. Continued precipitation shortfall in late summer and fall raises risk of delayed stream baseflow decline and vegetation stress typical of extreme drought.

Extreme drought (D3) covered 44.41 percent of Jefferson County in the week of September 15-21, 2026. Concentrated water stress limits dilution of pollutants and elevates temperature in streams, pressuring aquatic species that require clean, cool water as the drought persists into fall.

Jefferson County carries 2.03% of its area in exceptional drought (D4) as of the week ending October 19, 2026, with severe drought affecting 44.40% of the county. Exceptional drought conditions developed in mid-September after a largely dry water year, raising fire risk and water stress heading into late fall.

Month-to-date October precipitation at Ralston Reservoir has reached 1.3 in through October 20, running 0.6 in above normal, reversing months of below-normal precipitation and improving soil moisture into the second half of the water year. This comes after August and September both tracked below normal.

Mean daily high at Ralston Reservoir, 8 km away, has averaged 73.2°F over the past 30 days, 6.6°F above the normal of 66.6°F, while mean daily low has averaged 51.7°F, 9.3°F above the normal of 42.4°F. This sustained warmth follows an August that set records as the second warmest on the weather record and continues the temperature pattern noted earlier this fall.

March Browns mayflies were recorded on September 20, 2026 on Clear Creek, a genus of mayflies that requires clean, well-oxygenated water. Their presence confirms baseline water quality persists in the reach into autumn.

An American Rubyspot was observed on October 17, 2026 at 10th Street in Golden on Clear Creek. This damselfly prefers flowing clear water and its presence indicates maintained water quality. October is late in the flight season for this species in Colorado, marking the end of breeding season.

Red Crossbills were reported in two notable concentrations near Foothill Shrublands: 9 birds at Nissen Reservoirs on October 19 and 10 Ponderosa Pine type 2 birds at a yard on October 18, 2026. These seed-eating finches are moving downslope in fall 2026 as part of broader montane irruptions tied to variable cone availability and habitat changes.

Mean daily high over the past 30 days at Ralston Reservoir is 85.3°F, 7.1°F above normal, with mean daily low 60.6°F, 7.6°F above normal. This warm stretch follows an August high of 97°F on August 22.

Precipitation to date in September is 0.3 in at Ralston Reservoir, 0.6 in below the normal of 0.86 in. The preceding month of August 2026 was 0.4 in below normal, ranking as the 53rd driest August on record for Jefferson County since 1895.