Temperature structures of: the full 3D atmospheres based on 280 × 280 × 300 grids points (orange density plot); the average ⟨ 3D ⟩ atmosphere (solid black line); and the equivalent 1D LHD temperature structure (dashed black line) for the [Fe/H] = −2.0 (left) and [Fe/H] = −3.0 (right) high resolution atmospheres, for a single snapshot in time. Darker regions in the density plot represent areas in the 3D atmospheres with densely populated temperature regions for a given optical depth. Large temperature deviations exist between the ⟨ 3D ⟩ and 1D atmospheres in both the deep layers (log τ_ROSS> 1.0) of the star and in line forming regions at log τ_ROSS< −2.0, while in layers where T ~ T_eff, the ⟨ 3D ⟩ and 1D temperature structures are quite similar.