A theoretical limit to the windspeed of a tornado, based on the assumption of a tornado core with the thermodynamic characteristics of the pseudoadiabatic lapse rate and hydrostatic balance. The thermodynamic speed limit may be expressed in terms of CAPE as (2 CAPE)^1/2, where CAPE is the convective available potential energy. The thermodynamic speed limit is often exceeded, illustrating that nonhydrostatic effects are important.