Skewed July rain explains floods in some states, dry reservoirs in others

July's monsoon rains have significantly reduced India's overall rainfall deficit, yet an analysis of meteorological data reveals a starkly uneven distribution. While the country experienced a slight surplus in July, this was concentrated in a few regions and occurred on only 18 days, leading to devastating floods in some parts of the country and critically dry reservoirs in others.

The India Meteorological Department (IMD) reported that July's rainfall was 2.2% above the 1971-2020 average, a modest surplus that helped decrease the cumulative monsoon deficit from 31% in June to 10.5%. However, this surplus was driven by intense downpours on specific days. These 18 days received 34% more rain than average, while the remaining 13 days saw a 39% deficit.

This concentration of heavy rainfall is evident in the intensity data. Light and moderate rain deficits were observed at 4.9% and 6.2% respectively. Conversely, all categories of heavy rainfall combined showed a surplus of 12%. This indicates that July's surplus is almost entirely attributable to intense, heavy downpours occurring on a limited number of days.

The analysis further highlights the extreme nature of the month's weather. IMD classifies rainfall deficits of 60% or more as "large deficient" and surpluses of 60% or more as "large excess." In July, the areas experiencing "large excess" rainfall constituted 12.2% of the country, while those under "large deficient" conditions were nearly equal at 12.6%. This near-even split underscores the month's pattern of extremes, with significant flooding in some regions and severe dryness in others.