In May 2006, the rainfall was less than normal in central Brazil and more than normal in most parts of Pará, Tocantins and northern Roraima states of northern Brazil, in the northern and eastern parts of Nordeste and in the eastern regions of Rio Grande do Sul state. The incursion of the first cold air mass in this month, over Brazil, was responsible for the reduction of temperatures in southeastern and central-western regions of Brazil and southern Amazonia state, causing the so called "friagem".

The Sea Surface Temperature (SST) in the equatorial Pacific was near normal, however, some areas of negative SST anomalies continued to persist near South American coast. Nevertheless, the ENSO phase is considered neutral.

The number of hot spots or vegetation fires over the country increased to 1800 during the month, a substantial increase in relation to April situation of 800 hot spots, due to the reduction of rainfall in the central and southern parts of Brazil.

Most of the river basins have registered reduction in runoff (river discharge) values in relation to the previous month, in spite of more than normal rainfall in the northern portions of the Amazon and Tocantins basins. In the southern parts of Paraná river basin, in the Uruguay river basin and the southeastern Atlantic basin, drier conditions prevailed.

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