The numerical study of the pseudo transient thermal behavior of an earth-to-air heat exchanger (EAHE) for three cities in Mexico is presented. The climate conditions correspond to the warmest day in summer and the coldest day in winter for: extreme weather (Juarez city, Chihuahua), mild weather (Mexico city, D.F.) and hot weather (Merida, Yucatan). The simulations of the EAHE were done in an in-house code based on the finite volume method. Hourly simulations were done for four Reynolds numbers (100, 500, 1000, 1500) through one day. In Juarez city, the EAHE worked correctly for cooling and heating purposes during the whole day. For Merida and Mexico City the EAHE did not work during certain periods. The maximum cooling potential provided by the EAHE was 17.4, 10.2 and 10 degrees C in Juarez, Merida and Mexico City, respectively. The maximum heating potential provided by the EAHE was 6.3, 12.5 and 3.2 degrees C in Juarez, Merida and Mexico City, respectively. Such cooling and heating effects help to improve the thermal comfort inside a building located in this type of climates. (C) 2015 Elsevier B.V. All rights reserved.