Abstract Soil moisture is a key ingredient of humid heat through supplying moisture and modifying boundary layer properties. Soil moisture heterogeneity due to for example, antecedent rainfall, can strongly influence weather patterns; yet, its effect on humid heat is poorly understood. Idealized numerical simulations are performed with a cloud‐resolving (Δx= ${Delta }x=$ 500 m), coupled land‐atmosphere model wherein wet patches on length‐scales λ∈ $lambda in $ 25–150 km are prescribed. Compared to experiments with uniform soil moisture, humid heat is locally amplified by 1–4° ${}^{circ}$C, with maximum amplification for the critical soil moisture length‐scale λc= ${lambda }{c}=$ 50 km. Subsidence associated with a soil moisture‐induced mesoscale circulation concentrates warm, humid air in a shallower boundary layer. The background wind and the magnitude of the wet‐dry contrast control the relationship between λc ${lambda }{c}$ and the humid heat amplification. Based on observed soil moisture patterns, these results will help to predict extreme humid heat on city and county scales across the Tropics.