Chesapeake Rolling Coastal Plain

Mean daily high and low temperatures at Washington Reagan National Airport, 14 km from this area, ran 1.4°F and 3.8°F above normal over the past 30 days, averaging 74.3°F and 59.3°F respectively. October temperatures continue warmer than the 1991-2020 normal for these calendar days.

Great Spreadwing (threatened damselfly) observed October 8-13 in Arlington and Kensington. Tiger Spiketail (threatened dragonfly) recorded October 13. These species migrate southward in autumn; their October presence marks the annual fall movement to overwintering grounds.

Salt and Pepper Microcaddisfly and net-spinning caddisfly larvae recorded through October 16 in tributaries including the Potomac River system. These pollution-sensitive larvae require dissolved oxygen above 6 mg/L and indicate that some stream reaches maintain acceptable water quality despite regional impairment designations.

Virile Crayfish (invasive) recorded October 18 in Derwood and September 18 in Fairfax Station. This aggressive non-native competes with native crayfishes and alters benthic communities through predation, with continuous recent observations showing its ongoing spread through watershed tributaries.

Tidal water level at this location on October 20, 2026 at 15:12 was 0.467 m, standing 0.216 m above the predicted level. This elevated water level reflects spring tide conditions characteristic of late October, when tidal range is near maximum.

Green Treefrogs flagged as threatened under Virginia law were recorded at multiple locations through October 16, 2026, including Alexandria, Groveton, and Silver Spring. These observations confirm established populations in the region despite state-level conservation concerns.

A Monarch butterfly was observed on October 19, 2026, at Forest Glen in Silver Spring, Maryland. Monarchs are under proposed threatened status federally and threatened status in Virginia, making fall migration records significant during the window before hibernation begins.

Mean daily high and low temperatures at Washington Reagan National Airport, 14 km from this area, ran 3°F and 2.8°F above normal over the past 30 days, averaging 86.3°F and 69.1°F respectively. The period included a 98°F peak on September 1, contributing to heat stress on water bodies and aquatic life.

Montgomery County holds 4.66% of its area in Moderate Drought (D1) or worse as of September 21, steady for the past three weeks. While the drought footprint remains small, the stability suggests dry conditions may persist without significant rainfall.

September precipitation at Montgomery County averaged 2.3 in through mid-month, 1.3 in below the 1901-2000 normal of 3.6 in, ranking 40th driest of 131 September records since 1895. September this year is running notably dry compared to the normal pattern for the month in this region.