Understanding atmospheric stability throughout the wind turbine rotor layer is critical for predicting wake evolution, power production, wake steering performance, and structural loading. Here, we use sonic anemometer, profiling lidar, and thermodynamic profiler observations collected from an instrumented barge deployed during June–September 2024 as part of the Third Wind Forecast Improvement Project (WFIP3) campaign off the U.S. northeast coast to evaluate how well near-surface measurements represent atmospheric stability at wind turbine hub height. Surface-based and rotor-layer stability classifications disagree more than 30 % of the time, with the dominant decoupling regime characterized by unstable surface conditions beneath a stably stratified rotor layer. The frequency of these decoupling events increases through late summer into fall as hub-height stratification strengthens, while individual events become shorter-lived, indicating frequent transitions between coupled and decoupled states. Decoupling events are characterized by slower wind speeds consistent with weaker turbulent mixing through the marine boundary layer. Surface observations often fail to represent the atmospheric stability experienced by offshore wind turbines during summer marine conditions. Consequently, relying solely on near-surface measurements may underestimate the occurrence of stable rotor-layer conditions that influence wake behavior, offshore wind farm power performance, and estimates of structural loads.