Record high temperatures were documented in the McMurdo Dry Valleys, Antarctica, on March 18, 2022, exceeding average temperatures for that day by nearly 30°C. Satellite imagery and stream gage measurements indicate that surface wetting coincided with this warming more than two months after peak summer thaw and likely exceeded thresholds for rehydration and activation of resident organisms that typically survive the cold and dry conditions of the polar fall in a freeze-dried state. Such events may be a harbinger of future climate conditions characterized by warmer temperatures and greater thaw in this region of Antarctica, which could influence the distribution, activity, and abundance of sentinel taxa. Here we describe the ecological responses to this weather anomaly reporting on meteorological and hydrological measurements across the region and on biological observations from Canada Stream, one of the most diverse and productive ecosystems within the McMurdo Dry Valleys.