This dataset contains in situ observations of lake ice under a complete seasonal cycle. The study area is Lake Hanzhang in northeast China and the observation period is from winter 2020 to spring 2021. The observations include meteorological, hydrological and optical data. The files contain the following data fields: Readme – a detailed description of data Equipment list – instrument type and accuracy Meteorological data – air temperature, relative humidity, wind speed, pressure, surface temperature Solar radiation data – incident solar radiation and reflected solar radiation Ice thickness and snow depth – ice thickness (ice bottom) and snow depth (ice surface) Ice-water temperature – ice temperature and water ice temperature Spectral irradiance - incident (air) – incident spectral irradiance from 320 - 950 nm (air) Spectral irradiance - reflectance (air) – reflectance spectral irradiance from 320 - 950 nm (air) Spectral irradiance - incident (water - 70 cm to ice surface) – incident spectral irradiance from 320 - 950 nm (water - 70 cm to ice surface) Spectral irradiance - incident (water - 110 cm to ice surface) – incident spectral irradiance from 320 - 950 nm (water - 110 cm to ice surface)