A brief appraisal of the climatic and related agricultural hydrology aspects of Puerto Rico is discussed. In the tropics moisture and latent heat flux cycles are generally more critical than temperature (sensible heat flux) in contrast to these relationships at middle and higher latitudes. Yet, a continental-like climate is found in some interior valleys such as at Utuado, where the daily air temperature span is around 22°C in winter. A low level inversion (trade-wind inversion) is generally exhibited below 2 km, constituting a most important regulating valve of the general circulation here. Frequently, it acts as a strong lid opposing the vertical cloud development necessary to produce rainfall. This undesirable situation possibly makes things worse in the drier part of the year, pmducing wide statistical spread from the mean rainfall at that time. An appraisal of the Island's hydrology reveals a very unfavorable agricultural water balance for the south coast, in contrast to a decidedly better picture for the north coast. Nevertheless, during the past decade both the north and south coasts experienced a build-up of the most extreme drought conditions in the history of the island. The Palmer's Drought Index, which coincides with the gap between actual and potential evapotranspiration, shows that 1964, 1965, 1967, and 1968 were the most critical years. Application is made of the Crop Moisture Index (CMI) as a more detailed measure of drought in the time scale.