This U.S. Geological Survey (USGS) Data Release provides high resolution water temperature data collected at a long-term monitoring site in Dexter Reservoir, Oregon, USA, May 29 to July 20, 2014. All data are reported as raw measured values in degrees Celsius (C) and are not rounded to USGS significant figures. A distributed temperature sensing cable was used for high resolution measurement of water temperatures throughout the water column at the long-term monitoring site, which has persistent summer cyanobacterial blooms.