Data description : Data are temperature profiles recorded in Lakes Geneva, Bourget and Annecy during the summer period of strong thermal stratification. The dataset consists in one profile per year and it covers the periods 1974 to 2013, 1984 to 2013 and 1991 to 2013 for Lakes Geneva, Bourget and Annecy respectively.

Data acquisition : Temperature data were collected from the deepest point in the lakes. Temperature measurements were measured manually using thermometers and multiparameters probes. In Lake Geneva, water temperature was measured manually with a thermometer until 1990 from discrete depths of 5 to 10 meter intervals through 50 meter depth and approximately 50-meter intervals for the rest of the water column. After 1990 various multiparameter probes were used for temperature measurements, Meerestechnik Elektronik (1991-2001), CTD 90 (2002-2007), CTD 90M (2008-2011, 2013), and RBR (2012). In Lake Annecy, various multiparameter probes, including Meerestechnik Elektronik (1991-2001), CTD 90 (2003-2005), CTD 90M (2008-2011, 2013), and RBR (2012) were used for temperature measurements at depth intervals between 0.01 and 1.8 meters. Temperature profiles were measured in Lake Bourget at depth intervals between 0.01 and 10 meters using various multiparameter probes, including ISMA probe DNTC (1984-1985), Meerestechnik Elektronik ECO 236 (1986-1998), CTD SBE 19SeaCAT Profiler (1992-2002), and CTD SBE 19plus V2 SeaCAT (2003-2013).

Data processing : A single temperature profile was selected during the stable summer stratified period for each year and lake. The timing of the stable summer stratification was estimated by using the relative thermal resistance to mixing (Pilla et al. submitted). This metric was computed for all sampling dates from 1974 to 2013, 1984 to 2013 and 1991 to 2013 for lakes Geneva, Bourget and Annecy respectively. The median day of year with the highest thermal resistance to mixing was identified for each lake separately. The annual thermal profiles were selected within the time frame of ±21 days from the median day of year with the highest thermal resistance to mixing for each lake. The selected temperature profiles were linearly interpolated or binned to 0.5 m increments from surface to bottom.