Material surface time of wetness (TOW) and temperature (T) are criticalvariables that influence the corrosion behavior of reinforced steelbars in concrete, and concrete durability. In concrete structures, bothvariables are indirectly dependent on the atmospheric relative humidity/temperature complex, and specific structural characteristics: concretecomposition, water/cement ratio, curing time, geometry and orientationin the environment. Concrete internal TOW and T distribution data werecollected using Cu/Au electronic sensors arranged at 15, 40, 65 and 75mm depths in a concrete block (300 x 300 x 150 mm; w/c 0.5) exposedfor one year in a rural-urban humid tropical climate in southeast Mexico.Concrete internal TOW allows structure designers to define concretecover thickness over steel reinforcement bars. The results indicatethat under the tested exposure conditions, the side of the block withthe highest TOW values (west) would require a thicker concrete coverthan that with lower values (east). Longer TOW can increase the possiblepermeation of gases such as CO2, and consequent concrete carbonation,as well as lead to loss of the passive state in steel reinforcement andinitiation of the corrosion process.