The dataset contains the day of year for the onset and end of thermal stratification and its total length in Blelham Tarn, Esthwaite Water, Windermere, north basin and Windermere, south basin between 1951 and 2017. 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. Full details about this dataset can be found at https://doi.org/10.5285/d029bb43-5722-4932-9c14-be316a2e7144
