
This investigation on the time distribution of the rainfall in Bissau from 1971 to 2015 has shown that within this period a slowly decrement of the rainfall regime is going. This phenomenon is clearly visible by the end of the period where intensive rainfall with pluviometry greater or equal to 600 mm/month was becoming rare and rare. This situation calls the authorities of the country to take very important and urgent measures to reduce or even to stop its evolution as it seems to be the beginning.