Complex sentence: On January 13th 1999, Toronto called in the Canadian Forces to help with the Snowstorm of 1999 where, within twelve days, Toronto recorded 118.4 cm of snow, much of it lake effect from Lake Ontario.
Split into simpler sentences: On January 13th 1999, Toronto called in the Canadian Forces to help with the Snowstorm of 1999. During that time, in only twevle days, Toronto recorded 118.4 cm of snow, much of it lake effect from Lake Ontario.