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The U.S. Fish and Wildlife Service began extensively monitoring water temperature in the Klamath Basin in 2001 due to growing interest and concern over the effects of elevated water temperatures, particularly in relationship to Pacific salmonids. This report summarizes the results of water temperature monitoring for a set of locations within the Klamath River watershed that are accessible to anadromous fish for water years (WYs) 2020 and 2021. Temperature criteria for the Trinity River have been adopted by the Trinity River Restoration Program (TRRP) and are based upon the Trinity River Flow Evaluation Study and the Trinity River Mainstem Fishery Restoration: Final Environmental Impact Statement/Environmental Impact Report. We evaluated water temperatures on the Klamath River using the U.S. Environmental Protection Agency’s Pacific Northwest salmonid life history stage temperature criteria. Water temperature criteria for all focal sites evaluated were exceeded on the Trinity and Klamath rivers during WY 2020 and 2021. All five focal sites on the Klamath River set new water temperature records by surpassing the historical seven-day average daily maximum temperature in WY 2020 (range 2 to 16 days exceeded) and WY 2021 (range 12 to 41 days exceeded). On the Trinity River, the daily average water temperatures surpassed the maximum historical daily average water temperatures at three of the four focal sites in WY 2020 (range 30 to 41 days exceeded) and all four focal sites in WY 2021 (range 1 to 55 days exceeded). The 2020 and 2021 WYs were designated as ‘Critically Dry� by the TRRP. Although supplemental flow criteria of �23 � for migrating adult salmonids was exceeded, no emergency flows were released from either Iron Gate or Lewiston dams in WY 2020, however there was an emergency release in August from Lewiston Dam in WY 2021 in an attempt to reduce mainstem Trinity River water temperature and mitigate disease outbreak in adult salmonids. Some methods were corrected for historical water temperature data in the 2019 WY water temperature report. Calculations for days-criteria-were-exceeded may be different in reports prior to 2019.