The purpose of this study was to evaluatethe rainfall variability and to determine the frequency ofdroughts periods during the soybean cycle, in the Westernregion of the Paraná State. For that objective, were usedmeteorological data from 48 stations, distributed along theWestern of Paraná state, from 1976 to 2018. Rainfallvariability was analyzed in the annual, monthly and 10-daysscales, and the frequencies of droughts periods of 10 daysfrom September to March and >= 20 days during the year, andit was used the Climatological Water Balance (CLIMWB)during the cycle of soybean, according to the method ofThornthwaite and Mather. The Available Water Capacity(AWC) used was 20 mm. It was verified rainfall variabilityin area of the study, however with sufficient rainfall forsoybean cultivation requirements. The results of this study help to choose the best sowing times such that the most sensitive phases of soybean cycle occur in the lowest risk periods.