Moisture due to rainfall is required to be properly managed to avoid its destructive impact on flexible Pavement surface of Asphaltic Concrete. In spite of this consideration, Pavement continues to be exposed to rainfall all through the service life. Flexible pavements, tested and verified, show that during the service years of the Pavement, rainfall contributes to the deterioration and loss of strength, with duration of exposure. The statistical analysis of the results, employing empirical models, show that a linear correlation existed between loss of strength and duration of exposure to moisture (water) due to rainfall. This result was utilized to predict pavement maintenance programmes.