Data are collected at the Girnock Burn Littlemill River Temperature Monitoring Site (Eastings 332600, Northing 795700), which is the longest detailed (sub-daily) river temperature record in Scotland, beginning in 1968. Data were initially collected using a mechanical paper-based Cambridge Instruments thermograph. A digital datalogger was first deployed in 1984 and a variety of dataloggers have since been deployed at the site.

This dataset extends from 1 January 1988 to 21 November 2023 and contains minimal data breaks (e.g. where equipment malfunctioned so data were unavailable). The time series contains temperature measurements made by different combinations of datalogger makes and models. Earlier data (<1988) were removed due to a lack of suitable metadata (equipment type, site locations or sampling methods) or equipment from which to determine instrument bias. Depending on the datalogger make and model, measurements were taken at 15 minute or hourly intervals.

Data are stored in the Marine Directorate FLEObs database, alongside calibration information for more recent years (post 2010). Bias correction for earlier years (pre-2010) was undertaken through calibration experiments that accounted for systematic rounding errors associated with particular makes and models of instrument, but not for any additional biases associated with individual units (Jackson et al., 2025). The summary metrics published here (daily maximum, mean and minimum river temperature) are derived from the corrected raw resolution (i.e. 15 minutes or 1 hour) timeseries of 1 January 1988 to 21 November 2023.