The internal relative humidity (RH) during the setting, curing and service life is one of the factors that influences on the durability of any concrete structure. However, it does not show evidence of rebar deterioration since local corrosion products formed change the critical RH value. For this reason, the measurements of the RH in concrete, as many authors have stated in the literature, are not accurate enough to predict the development of the corrosion process. The time of wetness (TOW) and the moisture content are, however, more acceptable parameters to survey the structure durability. This paper discusses the information that the concrete internal temperature (T) and the TOW provide regarding durability, when changes in the external environmental parameters, the geometry of the structure and its orientation with respect to the sun take place. The monitored data are from concrete exposed to humid tropical atmosphere of Yucatan Peninsula, southeast of Mexico. Some of the results indicated that there are specific tendencies regarding geometry and orientation of the specimens. The TOW distribution found in this work would allow the structure designers to define the concrete thickness over the steel bars based on the orientation and geometry of the structural element and in terms of the direction in which the environmental parameters act.