The data show the long-term relative sea ice lead frequencies for the Arctic (November – April 2002/03 – 2018/19) and Antarctic (April – September 2003 – 2019), respectively. The data are projected onto the coordinate grid EPSG:3413 (ARC) and ESPG:3412 (ANT) at a spatial resolution of 1 km² and are stored as NetCDF4 files.Ice surface temperature data (MYD/MOD29 col. 6 [Hall and Riggers, 2015]) from the Moderate-Resolution Imaging Spectroradiometer (MODIS) are used to derive daily observations of sea ice leads in both polar regions. Sea ice leads are defined as significant local surface temperature anomalies and they are automatically identified during a two-stage process, including 1) the tile-based retrieval of potential sea ice leads and 2) the identification of cloud artefacts using fuzzy logic (see Reiser et al., 2020 for further details [Reiser et al., 2020]). Subsequently, all daily sea ice lead maps are combined to long-term averages showing the climatological distribution of leads in the Arctic and Antarctic, respectively. The dataset represents an update for the Arctic (Willmes & Heinemann, 2016 [Willmes and Heinemann, 2016]) and is the first for the Antarctic. These maps reveal, that multiple distinct features with increased lead frequencies are present that are related to bathymetric structures, e.g. the continental shelf break or ridges and troughs.