The highest temperature ever , recorded on 31 July 1983 , was 38.8 Â C ( 101.8 Â F ) , and the lowest was a â ' 20.7 Â C ( â ' 5.3 Â F ) reached on 1 January 1985 . The highest temperature ever , recorded on 28 July 1921 , was 40.3 Â C ( 104.5 Â F ) , and the lowest was a â ' 20.7 Â C ( â ' 5.3 Â F ) reached on 1 January 1985 .