<p>The Hailuoto Atmospheric Observations over Sea ice (HAOS) campaign took place at the westernmost point of Hailuoto island (Finland) between 27 February and 2 March 2020. The aim of the campaign was to obtain atmospheric boundary layer (ABL) observations over seasonal sea ice in the Bay of Bothnia. Throughout 4 days both fixed-wing and quad-propeller rotorcraft unmanned aerial vehicles (UAV) were deployed over the sea ice to measure the properties of the lower ABL and to obtain accompanying high-resolution aerial photographs of the underlying ice surface. Additionally, a 3D sonic anenometer, an automatic weather station and a Halo Doppler lidar were installed on the shore to collect meteorological observations. During the UAV flights, measurements of temperature, relative humidity and atmospheric pressure were collected at 4 different altitudes between 25 m and 100 m, over an area of ~ 1.5 km<sup>2</sup> of sea ice, located 1.1–1.3 km offshore from the Hailuoto Marjaniemi pier, together with orthomosaic maps of the ice surface below. Altogether the obtained dataset consists of 27 meteorological flights, 4 photogrammetry missions and continuous measurements of atmospheric properties from ground-based stations located at the coast. The acquired observations have been quality controlled and post processed and are available through the PANGAEA repository (<a href="https://doi.pangaea.de/10.1594/PANGAEA.918823"target="_blank">https://doi.pangaea.de/10.1594/PANGAEA.918823</a>, Wenta et al., 2020).