Actually, we have studied some procedures of the local rain in Porto Velho, Rondônia, With regard to the period 1945 - 2003, including the survey of the rainfall according to the shower and the series of occurrences on all events, in general. The main characteristics of the rainfall condition here are sue has. A rainy weather from Number to April with monthly rainfall between 228,9 mm, and 329,6 mm, and winter time from June to September with monthly rainfall between 38,9 mm, and 107,7 mm, and may and October are taken as transition months in the period. The tendency of pluvial precipitation in Porto Velho has been regular according to the number of occurrences as only 16 of them are out of parameters. The analysis of the distribution of the quarterly variability of the historical series of rain water, there was no quarterly tendency on the increase or decrease of medium values as there is a percentage of meaning magnitude between 62,7% and 79,78% in relation to dispersion measure. The period of years and quarters of rain water out of the variability of the dispersion measure has kept up with the phenomena El Niño and La Niña.
Statistical analysis; Seasonality; Tendency of the rainfall; Variability strip
