Possible weather and biological effects on the abundance of duskywings (Erynnis Schrank, 1804: Hesperiidae) at Roxborough State Park, Douglas County, Colorado are described over a five-year period (2018–2022). Of nine species reported from the park, four were consistently documented in all five years. Anomalous weather (temperature metrics and precipitation) in the summer of 2020 (and to a lesser degree in 2021), were coincident with abundance declines in E. telemachus Burns, 1960 in 2021 and 2022. Other relatively abundant Erynnis species demonstrated similar 2021 trends, however, E. brizo Boisduval & LeConte, [1837], E. afranius Lintner, 1878, and E. horatius Scudder & Burgess, 1870 all had relatively strong recoveries in abundance by 2022. Possible leaf palatability effects caused by an outbreak of tent caterpillars (Malacosoma californicum Packard, 1864, Family: Lasiocampidae) may have positively affected E. horatius second flight abundance in 2022.