Monthly actual ET (ETa) data estimated for the growing season (April - October) at 30-meter resolution with the Operational Simplified Surface Energy Balance (SSEBop) model (version 2.6) using satellite imagery obtained from Landsat 4, 5, 7, 8, and 9, and reference evapotranspiration obtained from the North America Land Data Assimilation 2 (NLDAS2) product for the Milk River basin, from 1985-2023. These data were collected to investigate the feasibility of incorporating remotely sensed evapotranspiration into an international water apportionment process between the U.S. and Canada.