Complex sentence: The best time to aerate a yard is in the fall time when the temperatures are starting to cool down during the daytime, this is also the best time since the ground is starting to receive more rain then in the hot summer months.
Split into simpler sentences: The best time to aerate a yard is in the fall time when the temperatures are starting to cool down during the daytime. This is also the best time since the ground is starting to receive more rain than in the hot summer months.