The destructive and Tama-predominant Yama waves reach the earth in greater proportion during the 120 days from Ashadha Pournima till Kartik Pournima. Their intensity is greater during this period. However, during this period of greater intensity (meaning, from Bhadrapad Shukla Chaturthi to Bhadrapad Shukla Chaturdashi), Ganesh waves too reach the earth in greater proportion. This helps reduce the intensity of the Yama waves.
On Shri Ganesh Chaturthi, as also during the days of Ganeshotsav, Ganesh Principle is a 1000 times more active on the earth. Worship of Shri Ganesh in this period bestows greater benefits.
(source : Sanatan Prabhat)