Field data and observations were obtained on the seasonal biology and ecology of Argynnis coronis simaetha in central Washington during 2013–24. Host plants, Viola trinervata, at a shrub-steppe site near Yakima produced new growth in late February–early March that hosted overwintered first instar larvae of A. coronis. Larvae and pupae completed development to adulthood in an estimated 56–86 days. Development was enhanced by ground micro-habitat temperatures 0.7–3.3 °C above ambient produced by heliothermic warming on 57–84 % of days during development. Adults eclosed from late April to late May and remained in the shrub-steppe for 4–6 weeks, with males nectaring primarily on Western Giant Hyssop, Agastache occidentalis. Females kept a low profile by being inactive and/or migrating westward to higher elevations soon after eclosion. Males joined the migration westward in mid-late June and both sexes were observed migrating along forest roads at 795–1740 m. Both sexes nectared in flowery mountain meadows and on ridges (2000–2200 m) in the Cascade Mountains during July–August with males more flight-active than females. During 2021–24, A. coronis males were found on nine occasions in the Olympic Mountains more than 200 km from the shrub-steppe. Both sexes migrated downslope eastward from the Cascades in mid-late August with predominantly females reaching the shrub-steppe in the last week of August and early September. A butterfly tagged in the Cascades in July 2015 was sighted 65 km to the east in Yakima in September. Returned populations in the shrub-steppe nectared on Rabbitbrush and oviposited during September–October with the last butterflies seen in mid-late October, 18–23 weeks after eclosion.