The Great Monsoon Retreat
October is defined by the withdrawal of the southwest monsoon, a process that doesn't happen overnight. It begins in the northwestern parts of the country, like Rajasthan, around early September and gradually moves southeast over several weeks. According
to the India Meteorological Department (IMD), the complete withdrawal from the entire country, including the southern peninsula, typically happens after October 1st. This retreat is marked by a significant reduction in humidity, clear skies, and a halt in rainfall for five consecutive days. As the low-pressure system over the northern plains weakens, it is replaced by a high-pressure system, causing the moist monsoon winds to recede.
Clear Skies and 'October Heat' in the North
For North India, including Delhi, Punjab, and Rajasthan, October ushers in some of the most pleasant weather of the year. The end of the monsoon means clear, sunny days and a welcome drop in humidity. However, this transition isn't always smooth. The period can be marked by a phenomenon known as 'October heat'. This occurs when clear skies lead to a rise in daytime temperatures, but the ground still holds residual moisture from the monsoon. This combination of heat and lingering humidity can feel oppressive for a short period before cooler, drier winter air properly sets in. By mid-October, nights become noticeably cool and pleasant, a signature of the post-monsoon season.
A Second Monsoon for the South
While most of India dries out, the story is completely different in the southeastern peninsula. October marks the beginning of the Northeast Monsoon, the primary rainy season for states like Tamil Nadu, parts of Andhra Pradesh, and Kerala. As the winds reverse direction, they pick up moisture over the Bay of Bengal and bring rain to the east coast. The normal onset date for this monsoon is around October 20. This season is crucial for the region's agriculture and water reservoirs, with Tamil Nadu receiving about 48% of its total annual rainfall during this period. Therefore, while the rest of the country packs away its umbrellas, South India prepares for significant rainfall, which can sometimes be intense and lead to flooding.
A Mixed Bag in Central and Western India
In Central and Western India, including states like Maharashtra, Gujarat, and Madhya Pradesh, October is a month of transition. The withdrawal of the southwest monsoon is well underway, leading to a significant decrease in rainfall and much clearer skies. Mumbai and the western coast see temperatures hover in the low 30s Celsius, and the oppressive humidity of the monsoon begins to recede. Much like in the north, this region can also experience a phase of 'October heat' due to high temperatures combining with leftover atmospheric moisture. Overall, the weather becomes progressively more comfortable, setting the stage for the mild winter ahead. According to recent IMD forecasts, the monsoon withdrawal is expected to be completed from most parts of central India in the first week of October.
Pleasant Days Return to the East
In Eastern India, including West Bengal, Odisha, and Bihar, the departure of the monsoon brings relief from months of heavy rain and high humidity. While some showers can linger in the early part of the month, the weather becomes predominantly dry and pleasant. In cities like Kolkata, daytime temperatures become more moderate, and the drop in humidity makes for comfortable conditions, which often coincides with the festive season. The Himalayan foothills in this region also see clear skies, making it an ideal time for travel and outdoor activities before the winter chill sets in. However, the Bay of Bengal remains a region to watch, as this period is also prone to the formation of tropical cyclones that can affect the eastern coast.
