the cincinnati–northern kentucky metropolitan area is located within a climatic transition zone. the southern area of the region, from roughly about the ohio river, is at the extreme northern limit of the humid subtropical climate; the north part of the region is on the extreme southern cusp of the humid continental climate. evidence of both humid subtropical climate and humid continental climate can be found here, particularly noticeable by the presence of plants indicative of each climatic region. within the area, the usda climate zone rating can vary from as warm as zone 6b to as cool as zone 5b, with the warmest areas tending to be found closest to the ohio river; individual microclimates of even cooler and warmer temperature may occur in the area but are too small to be considered in the overall climate zone rating. the common wall lizard, introduced from italy in the 1950s, is an example of fauna in the area that lends a subtropical ambiance to the urban core (near downtown cincinnati) area of the region.