 The county has a warm-summer humid continental climate ("Dfb") and average monthly temperatures in Somerset borough range from 24.5 °F in January to 67.1 °F in July.Somerset County is situated along the eastern border of the Allegheny Plateau physiographic province, which is characterized by gently folded to flat-lying sedimentary rocks of middle to late Paleozoic age.The eastern border of the county is approximately at the Allegheny Front, a geological boundary between the Allegheny Plateau and the Ridge and Valley Province (characterized by folded and faulted sedimentary rocks of early to middle Paleozoic age).