Complex sentence: The 2nd of September was the hottesy day in the month and the year in most areas, and tempratures reached in Bawtry, and this remains the hottest September temprature in the UK and the 8th hottest day of the 20th century.
Split into simpler sentences: The 2nd of September was the hottest day of the month as tempratures reached in Bawtry. This remains the hottest September temprature of any day in the UK and the 8th hottest day overall in the 20th century.