The average temperature is 10.2 Â C ( 50 Â F ) . The warmest month of the year is July ( 18.9 Â C or 66 Â F ) and the coldest month is January ( 1.6 Â C or 35 Â F ) . The warmest month is July ( 20 Â C or 68 Â F ) and the coldest is January ( 2.1 Â C or 35.8 Â F ) .