There are numerous reports in the literature of observations of land surface temperatures. Some of these, almost all made in situ, reveal maximum values in the 50°–70°C range, with a few, made in desert regions, near 80°C. Consideration of a simplified form of the surface energy balance equation, utilizing likely upper values of absorbed shortwave flux (≈1000 W m−2) and screen air temperature (≈55°C), that surface temperatures in the vicinity of 90°–100°C may occur for dry, darkish soils of low thermal conductivity (≈0.1–0.2 W m−1 K−1). Numerical simulations confirm this and suggest that temperature gradients in the first few centimeters of soil may reach 0.5°–1°C mm−1 under these extreme conditions. The study bears upon the intrinsic interest of identifying extreme maximum temperatures and yields interesting information regarding the comfort zone of animals (including man).