September 2026 Rainfall in Bihar and Jharkhand
Monsoon Trough, Bay of Bengal Depression and Southwest Monsoon Withdrawal Explained
September 2026 Rainfall in Bihar and Jharkhand
Introduction
As September approaches its end, India experiences an important seasonal transition: the withdrawal of the Southwest Monsoon. While rainfall gradually decreases in northwestern India, several eastern and southern states continue to experience significant rainfall.
During the third and fourth weeks of September 2026, a powerful weather system over the Bay of Bengal brought widespread rainfall and severe weather warnings to parts of Odisha, Andhra Pradesh and neighbouring states. Bihar and Jharkhand have also experienced rainfall activity during this period.
This situation raises an important geographical question: Why does heavy rainfall occur in some parts of India even after the Southwest Monsoon has started withdrawing?
The answer lies in understanding three interconnected atmospheric phenomena: the monsoon trough, the withdrawal of the Southwest Monsoon and the formation of low-pressure systems over the Bay of Bengal.
1. What Is the Monsoon Trough?
The monsoon trough is an elongated region of relatively low atmospheric pressure extending across northern India during the Southwest Monsoon season.
It is an important component of India’s summer monsoon circulation.
During the active monsoon season, the trough generally extends from northwestern India towards the northern Bay of Bengal, although its position changes considerably.
The monsoon trough plays an important role in determining the distribution and intensity of rainfall across the Indian subcontinent.
