Monsoon update: IMD issues heavy rainfall alert across India from August 16. Check state-wise forecast

India is staring at another spell of intense monsoon activity, with the India Meteorological Department (IMD) warning of heavy to very heavy rainfall across several parts of the country between August 16 and August 22.

The most significant threat is concentrated over eastern, central and northern India, where some areas could receive isolated extremely heavy rainfall, raising the risk of flooding, waterlogging, landslides and disruption to road and rail traffic.

The IMD's weather forecast bulletin said a well-marked low-pressure area over the northwest Bay of Bengal and adjoining West Bengal-North Odisha coasts was likely to move northwestwards and concentrate into a depression within the next 12 hours.

August 16-17: Odisha & West Bengal

The immediate concern is over Odisha and Gangetic West Bengal, where the IMD has forecast heavy to very heavy rainfall with isolated extremely heavy rainfall on August 16 and August 17.

On August 16, heavy to very heavy rainfall with isolated extremely heavy rainfall is likely at isolated places over Gangetic West Bengal and Odisha. Heavy to very heavy rainfall is also expected over Chhattisgarh, East Madhya Pradesh, Uttar Pradesh and Uttarakhand.

The threat continues on August 17, with heavy to very heavy rainfall and isolated extremely heavy rainfall again forecast over Gangetic West Bengal and Odisha. Arunachal Pradesh, Chhattisgarh, East Madhya Pradesh, Himachal Pradesh, Jammu & Kashmir-Ladakh, Jharkhand, Uttar Pradesh and Uttarakhand are also expected to see heavy to very heavy rain at isolated places.

The IMD has also identified a low to moderate flash-flood risk during the 24 hours up to 11:30 am on August 17 in several watersheds and neighbourhoods of Odisha and Gangetic West Bengal. In Odisha, the districts listed include Angul, Bargarh, Cuttack, Deogarh, Jagatsinghpur, Jajpur, Jharsuguda, Kendrapara, Keonjhar, Mayurbhanj, Puri and Sambalpur.

In Gangetic West Bengal, East Midnapore, Howrah, Jhargram, North 24 Parganas, South 24 Parganas and West Midnapore are under the flash-flood risk outlook.

August 18: Rain expands across north India & Delhi

The weather system's influence is expected to continue into August 18, with heavy to very heavy rainfall forecast at isolated places over Arunachal Pradesh, East Uttar Pradesh, Himachal Pradesh, Jammu & Kashmir-Ladakh, Jharkhand and Sub-Himalayan West Bengal & Sikkim.

Heavy rainfall is also likely over Assam and Meghalaya, Bihar, Chhattisgarh, East Madhya Pradesh, Gangetic West Bengal, Haryana-Chandigarh-Delhi, Punjab, Uttarakhand, West Uttar Pradesh and several northeastern states. Tamil Nadu, Puducherry and Karaikal are also expected to experience heavy rainfall at isolated places.

For Delhi-NCR, the broader forecast indicates fairly widespread rainfall on August 18, while West Uttar Pradesh is expected to see fairly widespread to widespread rain during August 16-17 and East Uttar Pradesh during August 16-22.

August 19: Heavy rain continues in the north and central regions 

On August 19, the IMD expects heavy to very heavy rainfall at isolated places over Jammu & Kashmir-Ladakh. Heavy rainfall is likely over Assam and Meghalaya, Bihar, East Rajasthan, East Uttar Pradesh, Himachal Pradesh, Madhya Pradesh, parts of the Northeast and Uttarakhand.

Tamil Nadu, Puducherry and Karaikal are also expected to receive heavy rain at isolated locations.

The IMD has separately warned of isolated very heavy rainfall over Jammu & Kashmir-Ladakh from August 17-19, Himachal Pradesh on August 17-18, Uttarakhand and West Uttar Pradesh on August 16-17, and East Uttar Pradesh on August 16-18.

August 20-22: Central India remains vulnerable 

The rain threat does not disappear after the first few days. On August 20, West Madhya Pradesh is forecast to receive heavy to very heavy rainfall at isolated places, while heavy rain is also expected over Assam and Meghalaya, Bihar, East Rajasthan, Himachal Pradesh, parts of the Northeast and Uttarakhand.

The situation remains active on August 21, when heavy to very heavy rainfall is again likely over West Madhya Pradesh. East Madhya Pradesh, East Rajasthan, Himachal Pradesh, Uttarakhand and parts of the Northeast could also receive heavy rainfall.

On August 22, heavy rainfall is forecast at isolated places over Assam and Meghalaya, East Madhya Pradesh, Himachal Pradesh, the Northeast and Uttarakhand.

The seven-day rainfall outlook shows fairly widespread to widespread rain continuing through much of the period in regions including the Northeast, East Uttar Pradesh, Uttarakhand, Himachal Pradesh, Jammu & Kashmir-Ladakh, Konkan and Goa, Kerala and Coastal Karnataka.

What is driving the rain? 

The IMD's analysis points to multiple weather systems working together. The well-marked low-pressure area over the northwest Bay of Bengal and adjoining West Bengal-North Odisha coasts was expected to move northwestwards and strengthen into a depression.

At the same time, the monsoon trough was extending from Amritsar and Ludhiana through Dehradun, Shahjahanpur, Varanasi, Daltonganj and Jamshedpur to the low-pressure area over the northwest Bay of Bengal.

The IMD also noted upper-air cyclonic circulations over northwest Uttar Pradesh, southeast Uttar Pradesh and adjoining areas, Gujarat, and Jammu division. Together, these systems are contributing to the widespread monsoon activity forecast across different parts of India.

Where the rain is expected to persist 

The broader seven-day forecast suggests that this is not a one-day weather event. East Uttar Pradesh, Uttarakhand, Himachal Pradesh, Jammu & Kashmir-Ladakh, parts of the Northeast, Konkan and Goa and Coastal Karnataka are among the regions where fairly widespread or widespread rainfall is expected across multiple days.

In the south, isolated to scattered rain is expected over Andhra Pradesh, Karnataka, Rayalaseema, Tamil Nadu, Telangana and other areas through August 22, while Kerala and Lakshadweep are expected to see fairly widespread to widespread rainfall through August 20, followed by scattered rain on August 21-22.