Indian summer monsoon rainfall
The Indian summer monsoon (June–September) brings most of India's annual rainfall, so its year-to-year swings matter for water, farming and livelihoods. Explore all-India monsoon rainfall since 1871, and how it relates to El Niño, the Indian Ocean Dipole (IOD) and North Atlantic sea surface temperature. Hover over a bar, or use the arrow keys, to read each season.
Drought year (deficient, below −10%) Flood year (excess, above +10%) Normal year (within ±10%) Faded: outside the highlight
El Niño La Niña Positive IOD Negative IOD Cold North Atlantic Warm North Atlantic
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Changing links with ENSO, the IOD and the North Atlantic
The running correlation between monsoon rainfall and June–September Niño 3.4, IOD or North Atlantic SST values, over a moving window. Negative values for Niño 3.4 mean El Niño years tend to be drier; positive values for the North Atlantic mean cold North Atlantic years tend to be drier. Values inside the grey band are not statistically significant at the 95% level.
Niño 3.4IODNorth Atlantic SST
About the data
- Rainfall, 1871–2019: all-India area-weighted June–September rainfall from the Indian Institute of Tropical Meteorology's homogeneous series (306 rain gauges), as % departure from its long-term mean of 880.6 mm (IITM Monsoon Online).
- Rainfall, 2020 onwards: India Meteorological Department end-of-season figures for the country as a whole, as % of the long period average (). The two sources use different station networks and normals, so values from 2020 onwards are not strictly continuous with earlier years.
- Categories follow IMD: deficient below 90% of normal, below normal 90–95%, normal 96–104%, above normal 105–110%, excess above 110%.
- El Niño and La Niña years: June–September mean Niño 3.4 SST anomaly (HadISST, via NOAA PSL), linearly detrended, at or above +0.5 °C (El Niño) or at or below −0.5 °C (La Niña).
- Positive and negative IOD years: June–September mean Dipole Mode Index (HadISST, via NOAA PSL), linearly detrended, at or above +0.3 °C or at or below −0.3 °C. The IOD usually peaks in autumn, so some events are weaker in these summer means.
- Cold and warm North Atlantic years: June–September mean SST averaged over 35°N–55°N, 310°E–340°E, following Borah et al. (2020, Science), who linked cold North Atlantic conditions to monsoon droughts outside El Niño years. Computed from NOAA ERSSTv5 (area-weighted, via ERDDAP) and linearly detrended; cold if at or below −0.5 standard deviations, warm if at or above +0.5.
The same Niño 3.4 and IOD series can be explored month by month in the climate index explorer. Data last updated on .