 The county has a warm-summer humid continental climate ("Dfb") and average monthly temperatures in Montrose range from 21.2 °F in January to 67.7 °F in July.As of the census of 2000, there were 42,238 people, 16,529 households, and 11,785 families residing in the county.The population density was 51 people per square mile (20/km²).