sentences:  McHenry County originally stretched all the way east to Lake Michigan, with the county seat centrally in McHenry, but in 1839, the eastern townships of the county were carved out to form Lake County.According to the U.S. Census Bureau, the county has a total area of , of which is land and (1.3%) is water.In recent years, average temperatures in the county seat of Woodstock have ranged from a low of in January to a high of in July, although a record low of was recorded in January 1979 and a record high of was recorded in July 1936.