 Union has a humid continental climate ("Dfa"/"Dfb") and average temperatures in Lewisburg range from 27.2 °F in January to 72.7 °F in July, while in Hartleton they range from 26.4 °F in January to 72.1 °F in July.As of the census of 2000, there were 41,624 people, 13,178 households, and 9,211 families residing in the county.The population density was 131 people per square mile (51/km²).