Southwest Monsoon 2026: End-of-Season Assessment

The Southwest Monsoon season, which extends from June to September, ended on 30 September 2026. The 2026 monsoon was characterised by below-normal and highly variable rainfall across the country, with considerable differences in rainfall distribution among regions and months. India as a whole received 759.4 mm of rainfall against the normal of 868.6 mm during the southwest monsoon season, resulting in a 12.6% deficit.

Figure 1: Meteorological subdivision-wise rainfall anomaly for the southwest monsoon season covering the period from 1 June to 30 September 2026. [Source: IMD]

Onset and advance of the monsoon

The southwest monsoon set in over Kerala on 4 June 2026, slightly later than its normal onset date of 1 June. It subsequently advanced across the country and covered the entire country by 9 July 2026, compared to the normal date of 8 July as shown in the IMD monsoon climatology.

The onset and advance of the monsoon, however, do not necessarily determine the seasonal rainfall performance. The 2026 season provides a good example of this, with the country experiencing substantial rainfall deficiency despite the monsoon covering the country on time.

Figure 2: Onset and advancement of the southwest monsoon of India during 2026. [Source: IMD]

Rainfall performance during June–September

The monsoon rainfall was highly variable from month to month. During June 2026, the country received 106.8 mm of rainfall against the normal of 165.3 mm, resulting in a 35.4% deficiency. Rainfall improved considerably during July, when the country received 283.3 mm, nearly the normal rainfall of 280.5 mm, with a 1.0% excess. Rainfall again remained below normal during August and September. The country received 213.3 mm in August against the normal of 254.9 mm, a 16.3% deficiency, while September received 155.1 mm against the normal of 167.9 mm, a 7.6% deficiency. As a result, the cumulative rainfall during the June–September 2026 southwest monsoon season was 759.4 mm, against the normal of 868.6 mm, resulting in an all-India seasonal rainfall deficiency of 12.6%.

                                

Regional rainfall distribution

The seasonal rainfall was highly heterogeneous across India. Among the four homogeneous regions, East & Northeast India recorded the largest seasonal rainfall deficiency (25.6%), followed by South Peninsular India (24.3%). Rainfall over Central India was close to normal, with a deficiency of only 2.6%, while Northwest India recorded a 5.9% deficiency.

The subdivision rainfall map (Figure 1) also illustrates the strong spatial variability. Some subdivisions experienced excess or near-normal rainfall, while several subdivisions in southern, eastern and northeastern India experienced substantial deficits.


Role of large-scale climate drivers

The monsoon season occurred under the influence of significant large-scale ocean–atmosphere variability, including El Niño conditions over the equatorial Pacific Ocean. During the season, El Niño conditions developed and strengthened over the equatorial Pacific Ocean, with above-normal sea-surface temperatures over the central and eastern equatorial Pacific. El Niño is an important large-scale climate driver that can influence the Indian summer monsoon circulation. The IOD remained broadly neutral.

These large-scale climate drivers provide an important background state, but they do not determine rainfall at every location. Monsoon rainfall is also strongly influenced by intraseasonal variability, monsoon low-pressure systems, atmospheric circulation, and other regional processes that shape rainfall distribution across different parts of the country.

Conclusion

The southwest monsoon arrived over Kerala on 4 June and covered the entire country on 9 July. The monsoon 2026 ended with an all-India rainfall deficiency of 12.6%. The season was marked by substantial temporal and spatial variability. A pronounced rainfall deficit during June was followed by near-normal rainfall in July, while rainfall again remained deficient during August and September.

The season also highlights the fact that monsoon rainfall distribution can vary considerably across time and space. A season can have a substantial rainfall deficit while individual locations and periods can still experience intense or extreme rainfall. Therefore, seasonal rainfall statistics should always be interpreted together with spatial distribution, temporal variability and rainfall intensity.

Note: The end of the southwest monsoon season on 30 September does not necessarily indicate that the southwest monsoon has completely withdrawn from the country. The withdrawal of the monsoon is determined separately by IMD based on prescribed meteorological criteria.

Featured Articles:

(i) El Niño, La Niña and the Indian Monsoon: A Climate Story from the Pacific Ocean to India

(ii) A Possible El Niño in 2026: What It Could Mean for the Indian Monsoon

(iii) Why Did the 1997 and 2015 Super El Niño Events Produce Different Indian Summer Monsoons?

(iv) El Niño Does Not Always Mean “No Rain” During the Monsoon: Can Better Water Management Reduce Its Impacts?

(v) What Does IMD's Probabilistic Monsoon Forecast Really Mean?

(vi) How IMD Declares the Monsoon Onset over Kerala and Monitors Its Advance Across India


Disclaimer: The views and interpretations presented in this blog are solely those of the author and are intended for educational and science communication purposes. They do not necessarily represent the official views, policies, forecasts, or positions of the India Meteorological Department (IMD) or any other organization with which the author is affiliated.





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