It is difficult to say what is the best time of year to visit the Pantanal. The climate is tropical, alternating between the rainy and dry seasons, which is characteristic of Central Brazil. The average temperatures vary between 17° C in the winter or dry season and 28° C in the summer or rainy season with a possible variation of 8° C.
Annual registered rainfall is high, generally between 1000 mm. and 1400 mm., but with a very uneven distribution through the year, getting heavy rains in the summer months (September to March) and prolonged dry spells in the winter (April to August). This turns the Pantanal unique in climatic and landscape diversity.
The rythm of the waters
Irrigated by the flood waters of the river Paraguai and its tributaries, the Pantanal of Mato Grosso do Sul transforms itself every six months.The heaviest rains falling on the head waters of the tributaries in the summer months (November to April) start the flooding season. The flooded areas form a dense network of lakes, bays and swamps linked by the permanent streams or by efemerant spill ways. After months of floods, when the whole of the Pantanal becomes submerged in a sea of fresh water, the water level starts to drop. When the lower lying areas dry out the soil reappears, nourished and invigorated, as fertile pastures and life explodes in living colors throughout the countryside. Several of the lakes and bays retain large numbers of fish when the spillways dry out. In the flood season, from December to March, with the intensity of the rains, a major part of the Pantanal becomes submerged. The Flora is fertilised by the nutrients carried down from the higher land while the animals take refuge on the ridges. As with all birds the Ibis (Tuiuiú) start building their nests. Just before (October and November) and after the floods (April to June), it does not rain. With the water levels low, you get the formation of lakes and catchment hollows from which thousands of fish have no escape, becoming a banquet for birds and alligators.
The dry season, July to September, is the best time of year for wildlife observation. The lack of rain causes the lakes to diminish, reveals the grass plains and facilitates travel.The plains are green with vast areas of fresh grass. As with all trees the “Piúva” bursts into flower.