Pantanal Weather
The weather is classified as a savanna climate, according to the Köppen classification. The basin has two distinctive periods of precipitation:
- dry from about April through September
- rainy with heavy rain from October through March, with 80% of the annual precipitation during the wet season.
The Pantanal floodplain could be categorized as a big receptor, given that the average precipitation is only 800mm, while the average precipitation in the surrounding highlands reaches 1,200mm annually. The rain rapidly drains into the Pantanal basin, where there is a reduced run-off bed resulting in a flooded plain. The inclination of the area is very low, about one-to-two centimeters per kilometer from north to south and about six-to-eight centimeters per kilometer from east to west, contributing to the wetland formation. It can be hot during the day, but the nights are fresh or cold. Summer begins as the rains come and the temperatures rise. A heavy rainfall can lower temperatures, but as soon as the rain stops the temperature rises again. The annual pluviometric rate varies from 1,000 to 1,400mm and December and January are the months with heaviest rains. In that period the Pantanal is humid and warm and it becomes a huge lagoon with rivers, bogs and small lagoons all intermingled.
The predominant climate is tropical, presenting well defined features concerning the dry and the rainy seasons. The minimum temperature is 12°C (54°F) and the maximum 34°C (93°F).
Dry Season
From April to September, during the dry season, the temperature is very agreeable and the rains scarce. In the 'pantaneira' region the landscape changes dramatically according to the two well defined seasons of the year: the dry and the rainy one. During the dry season, on the extensive fields covered by gramineous species and 'cerrado' vegetation, the water is scarce being restrained to the perennial rivers with defined beds, to the lagoons near those rivers and to some swampy lands in the lower areas of the plain. During this season temperatures range from 24°C (75°F) to 34°C (93°F).
Rainy Season
From November to March Pantanal has the flood period. The vegetation changes according to the kind of soil and inundation, and what takes precedence are species of 'cerrado' on the sandy lands - known as High Pantanal - and gramineous species on the clay lands of Low Pantanal. With the flood, the depressions are inundated and form extensive lakes, known as 'baías' (bays). Those bays, especially if alkaline, present an astonishing beauty with waters in different colors according to the algae that develop there, creating shades of green, yellow, blue, red or black. As the waters rise a voluminous quantity of organic material is carried by the stream throughout large distances. During the reflux those remains are settled at the margins and beaches of the rivers, lagoons and swampy areas, becoming fertilizing elements for the earth.
