Atmospheric stability is essential for wind farm performance. In this numerical work, we investigate the behavior of wind farm wake flow under the influence of atmospheric stability through lattice Boltzmann method-based large eddy simulation. Wind turbines are conceptualized as actuator line models, and the ground momentum and thermal flux within the atmospheric boundary layer (ABL) are represented using the Monin–Obukhov similarity theory. Several fundamental configurations were first simulated, including a single wind turbine under stratified ABL, and a wind farm under neutral ABL, to validate the present numerical framework. The work has then been extended to the study of wind farm performance under varying ABL conditions, including stable and convective environments. The atmospheric stability influence on wind farm performance is analyzed in detail by examining the time-averaged wake flow velocity profiles, turbulence intensity distribution, and temperature field. These quantities tend to stabilize after several turbine rows, with the wake velocity and turbulence intensity being 9% and 22% greater, respectively, in the stable case compared to the convective case. The turbulence kinetic energy (TKE) budget and vortex structure analysis reveal that the buoyancy forces dominate the TKE production in the convective condition, while vertical shear dominates under stable condition.