Thornthwaite climate classification indices are essential to interpret climate types in the state of the pantanal biome (Mato Grosso do Sul), simplifying calculation process and interpretation of climatological water balance by farmers. However, there are few studies found in the literature that characterize the climate of pantanel biome in different climatic scenarios. We seek to assess climate change using humidity index of Thornthwaite climate classification in pantanal biome. We used historical series of climate data from all 79 municipalities of Mato Grosso do Sul between 1987 and 2017, which were divided into microregions. Air temperature and precipitation were collected on a daily scale. Precipitation and potential evapotranspiration data allowed calculating water balance by the Thornthwaite and Mather method. We characterized all locations as wet and dry using aridity indices proposed by Thornthwaite. The global climate model used was BCC-CSM 1.1 developed at the Beijing Climate Center (BCC) with a resolution of 125 x 125 km. We used the scenarios RCP-2.6, RCP-4, RCP-6 and RCP-8.5 for analyzing 21st century projections (2041-2060 and 2061-2080 periods). Maps were generated from climate indices of Mato Grosso do Sul using kriging interpolation method with spherical model, one neighbor, and 0.25° resolution. The microregions showed different patterns regarding water balance components and humidity index. Humidity index had a mean of 15.94. The prevailing climate in the state of Mato Grosso do Sul is C2 (moist subhumid). The state of Mato Grosso do Sul has two well-defined periods during the year: a dry and a rainy period. Three climate types predominate in Mato Grosso do Sul and, according to the Thornthwaite classification, are B1 (humid), C2 (moist subhumid), and C1 (dry subhumid). Water characterization in Mato Grosso do Sul showed 234.78 mm year−1 of water surplus, 80.8 mm year−1 of water deficit, and 1,114.8 mm year−1 of potential evapotranspiration. Water deficit and potential evapotranspiration decrease as latitude increases. The climatic projections show, in all scenarios, reduce the area classified as umida in the state (B1, B2 and B3), besides adding the dry subhumid class (C1). The Scenario RCP 8.5 in 2061 - 2080 is the most worrisome situation of all, because the state can undergo major changes, especially in the pantanal biome region.