Complex sentence: The highest temperature ever recorded in Winnipeg (since commencement of record-keeping in 1873) was on 11 July 1936; and the hottest temperature recorded in the past 25 years was on 6 August 1988 and again on 1 August 1989.
Split into simpler sentences: The highest temperature ever recorded in Winnipeg (since commencement of record-keeping in 1873) was on 11 July 1936. The hottest temperature recorded in the past 25 years was on 6 August 1988 and again on 1 August 1989.