The Pacific Northwest of North America (PNWNA) experienced several extreme hydrometeorological events during 2021 including the early summer heat dome that led to damaging wildfires followed by a sequence of land-falling atmospheric rivers resulting in catastrophic floods. While the synoptic-scale patterns and the terrestrial hydrological responses to these extreme events are well known, scant information remains on how freshwater temperatures responded during these events. Here, we make use of an observational database of hourly freshwater temperatures at 552 sites spanning the PNWNA during 2021 to characterize their evolution during four extreme hydrometeorological events including two cold waves, the early summer heat dome, and the flood event in southwestern British Columbia and northwestern Washington. Analyses show that daily water temperature fluctuations of �0.8�C occurred during extreme warming/cooling episodes even when averaged over the entire PNWNA. The mid-February and late December cold snaps led to a general ~1�C decline in water temperatures, while during the summer heat wave water temperatures rose on average by 2.7�C. More modest changes occurred during the mid-November flood events, although 3-day warming of 1.3�C occurred just south of impacted areas. For 160 sites with long term records (?12 years), 429 and 84 daily high water temperature records occurred during the heat dome and the flooding event, respectively. The presentation will conclude with a discussion of the potential environmental and ecological impacts of rapid and widespread freshwater temperature fluctuations in response to extreme hydrometeorological events.