The Climate Classification Systems (CCS) play an important role to define the geographic boundaries and agroclimatic zone. Thus, the main aim of this paper was to determine and evaluate the Köppen and Thornthwaite and Matter (1955) climatic classification for the Southern mesoregion of Amazonas. The data have been collected throughout 10 years (April 2008 through April 2018) by the National Meteorological Institute (INMET) automatic weather stations installed in the municipalities of Humaitá, Apuí, Manicoré, Boca do Acre, and Lábrea, Amazonas State, Brazil. The results have shown that Köppen’s CCS has presented the same type and subtype of climate, to the entire analyzed region. Thornthwaite and Mather's (1955) classification showed greater sensitivity to thermal and water climate variation, totaling 4 (four) types and 5 (five) climate subtypes considering the information generated by the respective water balances such as water deficit and surplus, real and potential, which can serve as a subsidy for studies of land or arable areas. On the other hand, the Koppen classification indicated more general results that are better suited to the macroscale. In this way, the climate classification of Thornthwaite and Mather (1955) showed better accuracy than the Köppen method for the study region.