Complex sentence: The first snowfall of the season is usually recorded in late October, although significant snowfall usually does not occur until late November, although snow has been recorded as early as September 17 (in 1965).
Split into simpler sentences: The first snowfall of the season is usually recorded in late October, although significant snowfall usually does not occur until mid-to-late November. However, snow has been recorded as early as September 17 (in 1965).