Puerto Rico is located in the Eastern Caribbean, 2000 km from the Florida Coast. (18 15 N, 66 30 W). Despite the fact that the Island covers an area of 8,897 km^2, Puerto Rico's topography is very diverse and temperature and precipitation patterns vary greatly. The varying topography over such a small area, and the contiguous Caribbean Sea, inflict greatly in the amount of precipitation, which serves as scenario for land, sea and air interactions. Easterly trade winds prevail over Puerto Rico during much of the year. These trade winds interact with convectively induced events, such as sea breeze, producing heavy amounts of rainfall. Additionally, the varying topography plays a major role in producing rain by orographic lifting. Synoptic features such as tropical easterly waves, cyclones and upper-level lows, among others, provide copious amount of precipitation annually. The study analyses the spatial and temporal distributions of rainfall for Puerto Rico by using contour and spectral techniques. Blackman-Tukey Autospectral Analyses were conducted for 41 stations over the island for a 39-year period that extends from 1970 to 2008. Spectral peaks are observed within the period ranges of six and twelve months. These maxima represent an early and late rain seasons; the latter coincides with the Atlantic Hurricane Season. The data for this study was obtained from the National Weather Service (NWS) Cooperative Precipitation Network (COOP) and was made available by the National Climatic Data Center (NCDC) in Asheville, NC.