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Informist, Friday, Oct. 17, 2025

 

LATEST DEVELOPMENTS

The wet spell over India remained weak during the week as the southwest monsoon continued to withdraw from the country. The northern parts of the country saw drier weather this week, while parts of south India recorded a rise in rainfall intensity due to the onset of the northeast monsoon, which happened in tandem with the southwest monsoon withdrawal.

 

After stalling for two weeks — from Sept. 26 to Oct. 9 — the southwest monsoon withdrew from a large chunk of India this week. It finally retreated from the entire country on Thursday, a day after its normal date of withdrawal, which is Oct. 15. The monsoon's retreat sped up with many parts of the country recording no rainfall. The declaration of withdrawal depends on the fulfilment of certain criteria, which include the absence of rainfall over a region for at least a few consecutive days.

 

At the same time, conditions became favourable for the onset of northeast monsoon over the south-east peninsular region of India. Easterly and northeasterly winds set in over southern peninsular India and south and the adjoining central Bay of Bengal earlier this week, causing heavy to very heavy rainfall over parts of Tamil Nadu, Kerala, and some parts of Karnataka during the week. The onset of northeast monsoon was declared the same day the southwest monsoon withdrew. 

 

Weak weather systems, mostly cyclonic circulations, persisted over the country during the week, causing light spells of showers over a few parts of east, central, and west India. Thunderstorms accompanied by lightning and gusty winds were also recorded in these regions, though they were few and far between.

 

From Oct. 1–16, the country has received 59.3 millimetres of rainfall, 23?ove normal for the period, data from the India Meteorological Department showed.

 

In the coming week, northeast monsoon rains are likely to continue over parts of south peninsular India. Under the influence of an upper air cyclonic circulation over the Arabian Sea, a low pressure area is likely to form off the Kerala and Karnataka coasts, which is likely to intensify into a depression and cause a further rise in the spread and strength of rainfall over south India.

 

Following is the weekly all-India rainfall since the beginning of the southwest monsoon season (in millimetres):

 

Period	Actual	Normal	Variation (%)
Oct. 9-15	13.3	17.8	(-)25
Oct. 2-8	40.6	24.8	64
Sept. 25-Oct. 1	37.1	28.9	28
Sept. 18-24	35.2	36.4	(-)3
Sept. 11-17	43.0	40.2	7
Sep. 4-10	45.3	45.5	0
Aug. 28-Sept. 3	72.5	49.0	48
Aug. 21-27	71.6	52.3	37
Aug. 14-20	70.8	57.9	22
Aug. 7-13	46.2	61.7	(-)25
Jul. 31-Aug. 6	48.0	63.0	(-)24
Jul. 24-30	78.8	66.3	19
Jul. 17-23	57.3	66.7	(-)14
Jul. 10-16	58.1	65.1	(-)11
Jul. 3-9	73.7	58.3	26
Jun. 26-Jul. 2	64.3	53.9	19
Jun. 19-25	63.9	46.3	38
Jun. 12-18	45.1	40.5	11
Jun. 5-11	12.1	28.6	(-)58
Jun. 1-4	14.3	11.5	25

 

The following table gives homogeneous region-wise rainfall during Jun. 1-Sept. 30 in the country (in millimetres): 

 

States	Actual	Normal	Variation(%)
East & Northeast India	1,089.9	1,367.3	(-)20
Northwest India	747.9	587.6	27
Central India	1,125.3	978	15
South Peninsula	787.4	716.2	10
All India	937.2	868.6	8

 

MONSOON PROGRESS

This year, the southwest monsoon hit the Kerala coast on May 24, eight days ahead of its normal date of Jun. 1 and by May 29, the monsoon current covered southern and northeast India entirely, and parts of east and central India. However, after May 29, the monsoon was in a weak phase and resumed advancing only on Jun. 16. 

 

The monsoon covered entire India on Jun. 29, nine days before the normal date of Jul. 8. Normally, beginning Jun. 1, the southwest monsoon advances northwards and covers the entire country around Jul. 8.

 

The withdrawal of monsoon began three days ahead of its normal date on Sept. 14. The withdrawal paused for two weeks, from Sept. 26 to Oct. 9, before withdrawing completely on Oct. 16, a day after its normal date of complete retreat. Normally, monsoon starts withdrawing around Sept. 17, and completes withdrawal from the entire country around Oct. 15. 

 

ONSET CRITERIA

At present, the department uses criteria that was adopted in 2016 for declaring the onset of the monsoon over Kerala, which is based on the daily rainfall at 14 stations in Kerala and the neighbouring area, along with wind-field and outgoing long-wave radiation over the southeast Arabian Sea.

 

If, after May 10, 60% of the 14 designated stations--Minicoy and Amini in Lakshadweep, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, and Kannur in Kerala, and Kudulu and Mangalore in Karnataka--report rainfall of 2.5 millimetres or more for two consecutive days, the onset over Kerala will be declared on the second day, provided the wind-field and outgoing long-wave radiation conditions are met.

 

The outgoing long-wave radiation measures the amount of terrestrial radiation released into space and, by extension, the amount of cloud cover and water vapour that intercepts that radiation in the atmosphere.

 

The criteria emphasise the sharp increase in rainfall over Kerala along with the setting up of large-scale monsoon flow and extension of westerlies up to 600 hectopascal. 

 

However, the department declares the monsoon onset or progress dates for other regions operationally in a subjective manner, considering the sharp increase in rainfall and its characteristic sustenance for a few days and associated changes in the atmospheric circulation features.

 

LONG-RANGE FORECAST

For October, the weather department has forecast above-normal rainfall for the country at 115% of the long-period average. Most parts of India are likely to receive normal to above-normal rainfall during October. However, some areas in northwest India, the extreme south of peninsular India and isolated pockets in northeast India may experience below-normal rainfall, it said.

 

Normal to below-normal maximum temperatures are likely over most of India in October, except in the northeast and adjoining east India, the western Himalayan states, and Saurashtra and Kutch.

 

The weather agency said there is a 71% chance of the La Nia conditions forming during Oct-Dec. However, the current sea surface temperatures over the equatorial Pacific are near average, indicating neutral El Nio-Southern Oscillation. The El Nino-Southern Oscillation refers to the fluctuation between El Nino and La Nina conditions in the Pacific Ocean. El Nino, which means Little Boy in Spanish, is a climate pattern marked by an unusual warming of the surface waters in the Pacific, leading to drier and hotter weather in India. La Nina, which means Little Girl in Spanish, is the opposite of El Nino. It is an oceanic and atmospheric phenomenon that is associated with colder sea surface temperatures. La Nina is usually associated with good rains in India.

 

There are also weak negative Indian Ocean Dipole conditions prevailing. The weather bureau said that negative Indian Ocean Dipole conditions are expected to continue beyond the southwest monsoon season. A negative Indian Ocean Dipole results in less rainfall in India, whereas a positive index leads to increased rainfall.

 

The department's long-range forecasts are as follows:

 

Region	Date	Period	Forecast (% of LPA)	Forecast (in mm)	Normal (mm)	Model error
All India	Sept. 30	Oct	115%	86.71	75.4
All India	Aug. 31	Sept	109	183	167.9
All India	Jul. 31	Aug	94-106	240-270	254.9
All India	Jun. 30	Jul	106	297.22	280.4
All India	May 27	Jun	108	178.52	165.3
All India	May 27	Jun-Sept	106	922.2	870.0	4%
All India	Apr. 15	Jun-Sept	105	913.5	870.0	5%

 

Private forecaster Skymet has predicted a "normal" southwest monsoon at 103% of the long-period average with an error margin of plus or minus 5%. The agency had predicted a weak start to the monsoon this year but expects the rainfall to increase from July. It does not see any chance of the occurrence of El Nino.

 

PRE-MONSOON RAINFALL

While the monsoon arrived on May 24, the weather department said rainfall during May would not be factored into the southwest monsoon. The country received above-normal rainfall during the pre-monsoon period in Mar-May. India received 185.8 millimetres of rainfall during Mar-May, 42?ove the normal for the period. Last year, it received 108.7 millimetres of rainfall during Mar-May, 8.1?low the normal for the period.

 

RECAP 2024
The country received 934.8 millimetres of rainfall in Jun-Sept last year, which was 108% of the long-period average. The monsoon hit the Kerala coast on May 30, two days ahead of the scheduled date, and covered the entire country by Jul. 2, six days ahead of the normal date of Jul. 8. The weather bureau's forecast for the monsoon onset over Kerala last year was May 31 and predicted rainfall during Jun-Sept 920.7 millimetres, or 96% of the long-period average.     

 

Overall, monsoon rainfall was above normal for the season and the spatial distribution was uniform. The rainfall in June was below-normal at 89% of the long-period average. However, the country received above-normal showers during the rest of the southwest monsoon period. Rainfall was 109% of the long-period average in July, 115% in August, and 112% in September.

 

Rainfall during the season was 107% of the long-period average in northwest India, 119% in central India, 86% in east and northeast India, and 114% in the southern peninsula. Of the total 36 meteorological subdivisions, two subdivisions received large excess, 10 received excess, and 21 recorded normal rainfall. Three subdivisions received deficient rainfall during Jun-Sept last year – Arunachal Pradesh, Punjab, Jammu & Kashmir, and Ladakh.

 

RESERVOIR LEVELS

The water level in 161 reservoirs across the country was 165.312 billion cubic metres as of Thursday, down nearly 1% from 166.74 cubic metres a week ago, as per data released by the Central Water Commission. 

 

The current level is 91% of the total live storage capacity of 182.48 billion cubic metres. The water level in the reservoirs as of Thursday was nearly 114.8% of the 10-year average. 

 

The water level in key reservoirs in eastern India was 17.664 billion cubic metres as of Thursday, down over 4% from 18.48 billion cubic metres recorded on Oct. 9. The current water level is over 81.18% of the total live storage capacity, down marginally from a year ago.

 

In the southern region, the water level was at 49.301 billion cubic metres as of Thursday, up from 49.14 billion cubic metres the previous week. The storage was nearly 90% of the total live storage capacity across the 45 reservoirs in the region, compared with over 87% a year ago. In the western region, reservoirs held 36.37 billion cubic metres, slightly down from 36.57 billion cubic metres the previous week. The storage as of Thursday was 97.3% of the total live storage capacity, slightly higher than 97% a year ago. 

 

The water level in reservoirs in the central region was 44.746 billion cubic metres, down from 45.24 billion cubic metres a week earlier. The current storage accounts for over 92% of the total live storage capacity, compared with 90% a year ago. However, water levels in reservoirs of the northern region declined to 17.235 billion cubic metres as of Thursday down from 17.30 billion cubic metres the previous week. The current level is over 87% of the total live storage capacity, higher than 65.4% a year ago. 

 

Of the 161 reservoirs, 155 reservoirs reported more than 80% of normal storage, and six had 80% or less.

 

SOWING

Farmers across the country have sown kharif crops over 112.15 million hectares as of Oct. 3, largely steady from 112.07 million hectares sown during the previous week as the season has almost ended, according to the agriculture ministry. On a yearly basis, the area under kharif crops as of Oct. 3 was up 0.6% from 111.5 million hectares sown during the same period last year.

 

Paddy acreage has risen over 1% on year to 44.2 million hectares as of Oct. 3. The area under pulses was also up over 1% on year at 12 million hectares. The area under urad was up 6.6% on year at 2.4 million hectares, while that under moong was largely unchanged on year at 3.5 million hectares. The area under tur was 4.7 million hectares, slightly up from 4.6 million hectares during the corresponding period last year.

 

The area under coarse cereals, promoted as "Shri Anna" by the government, was up over 6% at 19.5 million hectares, mainly supported by a rise in the area under maize. Maize acreage has risen 12.6% to 9.5 million hectares. The area under jowar was down 1% at 1.4 million hectares. The area under bajra has fallen slightly to 6.8 million hectares.

 

The area under oilseeds has declined 5.3% on year to 19.0 million hectares. The area under soybean, the largest kharif oilseed, dipped to 12.0 million hectares from nearly 13.0 million hectares a year ago. Groundnut acreage has fallen to 4.8 million hectares from 5.0 million hectares a year ago.

 

Similarly, the area under cotton has fallen nearly 3% on year to around 11 million hectares. The area under sugarcane has risen over 3% on year to 5.9 million hectares.

 

TERMS

LARGE EXCESS: Percentage departure of actual rainfall from normal rainfall is 60% or more 

EXCESS: Percentage departure of actual rainfall from normal rainfall is 20-59% 

NORMAL: Percentage departure of actual rainfall from normal rainfall is -19% to +19%

DEFICIENT: Percentage departure of actual rainfall from normal rainfall is (-)59-20%

LARGE DEFICIENT: Percentage departure of actual rainfall from normal rainfall is (-)99-60%

NORMAL: Percentage departure of actual rainfall is within +/-10% of the long period average

BELOW NORMAL: Percentage departure of actual rainfall is <10>

ABOVE NORMAL: Percentage departure of actual rainfall is within >10% of the long period average

EXCEPTIONALLY HEAVY RAINFALL: Rainfall realised in a day is a value near about the highest recorded rainfall at or near the station for the month or season. However, this term will be used only when the actual rainfall amount exceeds 120 mm. 

EXTREMELY HEAVY RAIN: Amount of rainfall realised in a day is >/= 244.5 mm

VERY HEAVY RAIN: Amount of rainfall realised in a day is 124.5-244.4 mm

HEAVY RAIN: Amount of rainfall realised in a day is 64.5-124.4 mm

MODERATE RAIN: Amount of rainfall realised in a day is 7.6-35.5 mm 

RED ALERT: Very heavy rainfall of over 204.4 mm in 24 hours

ORANGE ALERT: Heavy rainfall of 115.6-204.4 mm in 24 hours 

YELLOW ALERT: Warning to be aware of worsening weather conditions that could disrupt daily life

 

Internet links:
India Meteorological Department - www.imd.gov.in
National Centre for Medium Range Weather Forecasting - www.ncmrwf.gov.in
Indian Institute of Tropical Meteorology - www.tropmet.res.in. 

 

Reported by Shreya Shetty

Edited by Tanima Banerjee

 

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