Flat to Rolling Plains

Rocky Mountain Arsenal National Wildlife Refuge covers 14,948 acres under federal management with GAP 2 protection, meaning it is actively managed for biodiversity. However, the surrounding landscape is dominated by 1,158 GAP 4 units and 5 GAP 3 lands with no or minimal biodiversity mandates, including state resource management areas, local parks and military land that together comprise most protected holdings in the region.

October 2025 precipitation totaled 0.4 inches, 0.7 inches below the 1901-2000 normal of 1.1 inches and ranking 36th driest in the 131-year county record. The entire Denver County remains in Moderate Drought or drier as of the week ending October 26, 2026, with 100% of the county in D2+, reflecting sustained water stress.

Red Speckled Dun mayflies were recorded on October 20, 2026 at Prairie Loop Nature Trail in Greenwood Village. This pollution-sensitive mayfly indicates clean, well-oxygenated water, marking water quality suitable for aquatic insect communities.

North American River Otter recorded October 10, 2026 at Water Street and 7th Street in Denver, a casual sighting at an urban waterfront on the South Platte River. This threatened species persists in urban stream corridors despite habitat fragmentation.

Monarch butterflies recorded October 21, 2026 at Washington Park, Denver and October 20 at Pipeline Trail, Aurora. These sightings mark peak southbound migration when monarchs travel toward Mexican wintering grounds. Monarchs are listed as proposed threatened under federal law.

New England aster (Symphyotrichum novae-angliae) is in open flower as of 2026-10-21. This late-season bloom occurs within an October that has averaged 3.1°F above normal, making it the 15th warmest October on Denver County record, which may extend the bloom window into late autumn.

Extreme drought (D3) affected 50.86% of Denver County in mid-September but dropped to 0.15% as of the week of 2026-10-20 to 2026-10-26. This four-week decline represents major relief from the cumulative water stress that constrained vegetation growth through late summer and early fall.

Evening Grosbeaks were recorded multiple times in the last three days with counts of 18 at Plaster Reservoir on October 22 and 8 at Cherry Creek State Park on October 20. These irruptive migrants move south in fall when food becomes scarce in their northern breeding grounds, making October the expected time for downslope movements in Colorado.

Pallid sturgeon, whooping crane, and three other ESA-listed species have ranges overlapping this area. The piping plover, Ute ladies'-tresses, and western prairie fringed orchid are listed as threatened; no designated critical habitat overlaps the area.

The past 30 days averaged 90.8°F highs and 60°F lows at Denver Water Department, 6°F and 5.4°F above normal respectively, with a peak of 100°F on August 22. September 2025 averaged 64.5°F, 2.4°F above the 1901-2000 normal of 62.1°F and ranking 35th warmest in the 131-year record. Sustained above-normal temperatures compound evaporative losses during a drought period when precipitation is also below normal.