Description: The data publication contains supplementary data to the article "Supplementary Dataset to: The catastrophic thermokarst lake drainage events of 2018 in northwestern Alaska: Fast-forward into the future" This data publication includes four datasets: 1. Lake change datasets for 1999-2014 and 2017-2018 based on Landsat and Sentinel-1 data as Polygon Shapefiles 2. Lake change datasets for 2017 and 2018 based on high-temporal resolution PlanetScope imagery as Polygon Shapefiles and csv. 3. Lake ice simulations for the study area for 1980-2018. 4. Study sites in two versions: a) including seawater and b) clipped to land area. Files are Polygon Shapefiles. The datasets cover the land area of the Baldwin Peninsula and northern Seward Peninsula in north-western Alaska. The datasets are (#1&#2) remote sensing based observations and (#3) modelled data. Methods are described in detail in the original manuscript (open access). Dataset #4 is the extent of the study site in two versions, a) full extent including seawater and b) land only including lakes. The land boundary was clipped with the “Global Self-consistent, Hierarchical, High-resolution Geography Database” (GSHHG; Wessel and Smith, 1996) dataset in scale “h”. The datasets cover different temporal periods and have a different temporal resolution. Data were collected to measure the extent of a rapid and widespread thermokarst lake drainage event in northwestern Alaska in 2018 and to compare the affected number of lakes and area to previous periods. Lake-ice model data were calculated to simulate lake-ice conditions since 1980 and to put the lake-ice and weather conditions in 2017/2018 into context.