Post-Monsoon Season

October–December: the transition between the southwest monsoon and winter. The most dangerous cyclone season in the Bay of Bengal.

phenomena

What is the Post-Monsoon Season?

The post-monsoon season (October–December) is the transitional period between the southwest monsoon (June–September) and winter (December–February) across South Asia. It is one of the four official seasons recognised by the India Meteorological Department (IMD):

Winter — January and February
Pre-monsoon — March to May
Southwest monsoon — June to September
Post-monsoon — October to December

Across most of India, post-monsoon brings declining rainfall, gradual cooling and clear skies. But two phenomena make this season distinctive and often dangerous:

The Northeast Monsoon delivers Tamil Nadu, southern Andhra Pradesh, Kerala (eastern slopes) and Sri Lanka their main annual rainfall.
The Bay of Bengal becomes a cyclone factory, producing some of the deadliest tropical cyclones in human history.

The Northeast Monsoon

While most of India is drying out in October, a different rainfall system takes over the southern peninsula. As the southwest monsoon retreats, winds reverse direction, blowing from the northeast across the Bay of Bengal. These winds pick up moisture and dump it on the east coast of southern India and Sri Lanka.

Northeast Monsoon contributes:

48% of Tamil Nadu’s annual rainfall (vs 32% from the southwest monsoon).
75% of southern Andhra Pradesh’s rainfall.
80% of Sri Lanka’s northern and eastern rainfall.

Without the Northeast Monsoon, Chennai — India’s fourth-largest city — would face perennial water shortages. The 2015 Chennai floods (1,049 mm in one week) and the 2023 Cyclone Michaung were both Northeast Monsoon events.

Bay of Bengal cyclone season

The Bay of Bengal produces some of the most powerful and deadly tropical cyclones in the world. Of the world’s 35 deadliest cyclones in recorded history, 26 occurred in the Bay of Bengal. Most of these formed during the post-monsoon (October–November).

Why is post-monsoon the peak cyclone season?

Sea-surface temperatures remain 28–30°C — well above the 26.5°C threshold for cyclogenesis.
Monsoon winds weaken, reducing the wind shear that would otherwise tear storms apart.
Upper-atmosphere conditions favour vertical development.
Madden-Julian Oscillation (MJO) phases often align supportive in October–November.

Historical post-monsoon cyclones:

1970 Bhola Cyclone (12 November) — 300,000–500,000 deaths in East Pakistan (now Bangladesh). The deadliest cyclone in history.
1999 Odisha Super Cyclone (29 October) — 10,000+ deaths.
2007 Cyclone Sidr (15 November) — 3,400+ deaths in Bangladesh.
2008 Cyclone Nargis (2 May, atypically early) — 138,000+ deaths in Myanmar.
2013 Cyclone Phailin (12 October) — Category 4; mass evacuations limited deaths to ~45.
2014 Cyclone Hudhud (12 October) — Vizag battered; ~120 deaths.
2020 Cyclone Amphan (20 May, early monsoon).
2020 Cyclone Nivar (25 November) — Tamil Nadu.
2023 Cyclone Michaung (5 December) — Chennai’s third major flood event in eight years.

Post-monsoon weather across South Asia

The character of post-monsoon varies dramatically by region:

North India (Delhi, Punjab, Haryana, UP, Bihar)

Dry, clear, cool. Daytime 30→25°C, nights 20→12°C.
Stubble burning in Punjab + still-air conditions → severe November–December smog.
Diwali fireworks add to pollution peak.

Central India (MP, Maharashtra, Chhattisgarh)

Final monsoon rains taper in early October.
Pleasant October–November before winter sets in.

East India (West Bengal, Odisha, Bihar)

Major cyclone-impact zone.
Kolkata: 30°C → 22°C over October–November.

South India (Tamil Nadu, AP, Karnataka, Kerala)

Active Northeast Monsoon — wet, often stormy.
Chennai: heavy rain peak November.
Risk of flooding when cyclones combine with NEM rains.

Bangladesh

October typhoon/cyclone risk in southern coastal districts.
Dhaka: gradual cooling 30→25°C.

Pakistan

Karachi: 35→30°C. Mostly dry.
Northern areas begin first snow at high elevations.

Travel and farming in post-monsoon

For tourists, post-monsoon (especially October–November) is the single best travel window for most of India:

Clear skies after the rains.
Pleasant temperatures (25–30°C daytime).
Lush green landscapes.
Festival season (Durga Puja, Diwali, Eid-e-Milad).

For farmers, post-monsoon is the rabi (winter crop) sowing season:

Wheat sown October–November in north India.
Pulses, mustard, gram across central India.
Northeast Monsoon supports rice and pulses in Tamil Nadu.

Frequently asked questions

What months are the post-monsoon season? October, November and most of December. The IMD formally defines post-monsoon as October–December. November is the peak Bay of Bengal cyclone month.

Is it safe to travel to South India during post-monsoon? For most of India, post-monsoon is the best travel season. But Tamil Nadu, southern Andhra Pradesh and coastal Odisha/Bengal face cyclone risk during November. Check IMD forecasts and tropical-cyclone bulletins before booking.

Why is post-monsoon air quality so bad in north India? A combination of (1) stubble burning in Punjab and Haryana, (2) still calm air with temperature inversions, (3) Diwali firecracker emissions, and (4) increased domestic heating. Delhi PM2.5 routinely exceeds 300 µg/m³ in November.

Are post-monsoon cyclones getting more frequent? The total number of cyclones in the Bay of Bengal has not increased significantly, but the proportion that intensify to severe and very severe categories has risen. Climate scientists attribute this to warmer sea-surface temperatures.

Where can I check post-monsoon weather for my city? Mausam Online shows live weather, AQI and cyclone advisories on every city page. See Chennai, Visakhapatnam, Bhubaneswar, Kolkata, Delhi, Dhaka.