The data available to download comprise hypolimnion temperature (TEMP) in degrees Celsius, and hypolimnion dissolved oxygen concentration (DO) in mg per litre. All data have been measured in a depth of 13.5 to 15 m. All data are from January 2005 until the end of 2009. This is part of a long-term monitoring dataset from fortnightly sampling at Esthwaite Water in Cumbria, England. The data have been collected by the UK Centre for Ecology & Hydrology (UKCEH). This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability.