Bengaluru logs driest southwest monsoon in two decades, IMD data show

Despite a spate of heavy downpours in recent days, Bengaluru has endured one of its driest southwest monsoon seasons in years. India Meteorological Department (IMD) data for the core monsoon period from June 1 to September 30 show a sharp shortfall in seasonal rainfall across the city and much of Karnataka, with officials attributing the deficit to strong El Nino conditions that delayed the onset and weakened the rains.

Seasonal totals show stark shortfall in the city

At the IMD’s Bengaluru city observatory, cumulative rainfall during the southwest monsoon season stood at 313 mm, a departure of 236 mm below normal for the period. Station-wise figures across the urban agglomeration underscore the uneven but deficient pattern: the HAL station recorded 434 mm, a deficit of 29 mm, while Kempegowda International Airport measured 391 mm (with the corresponding deficit figure not immediately available).

The headline shortfall comes even as parts of the city witnessed intense showers toward the end of September, illustrating how late-season spells were insufficient to bridge the substantial gap accrued over the monsoon’s four months.

Twenty-year low at city observatory

A widely shared post on X highlighted the significance of the IMD city readings. “The IMD observatory at Bengaluru sees the driest southwest monsoon in 20 years by recording just 313.3 mm of rainfall against an average of 597.7 mm for the period between Jun 1st to 30th Sept. Previously the observatory had recorded 298.3 mm in the SWM season of 2006,” @BngWeather posted on X.

Statewide picture: Deficits across districts

IMD’s seasonal cumulative data indicate Karnataka as a whole received 564.6 mm of rain against a normal of 831.8 mm, reflecting a 32% shortfall. The deficit was widespread and, in some districts, severe.

Among districts, Bengaluru South (earlier Ramanagara) registered the steepest deficit at 87% below normal. Kalaburagi and Hassan followed with deficits of 55% and 53%, respectively. Bengaluru Urban district recorded 258.7 mm against a normal of 452.4 mm, amounting to a 43% deficit for the season.

Monsoon performance by meteorological subdivision

Karnataka’s three meteorological subdivisions all ended the season significantly below average:

• Coastal Karnataka received 2,228.3 mm against a normal 3,093.9 mm (28% below normal).
• North Interior Karnataka registered 329.8 mm against 480.8 mm (31% below normal).
• South Interior Karnataka logged 433.7 mm against 678.4 mm (36% below normal).

El Nino blamed for weakened rains

IMD officials linked the widespread shortfall to the ongoing El Nino event, which is known to suppress monsoon rainfall over parts of India and alter typical circulation patterns. “As forecast, we are witnessing strong El Nino conditions which has severely impacted the southwest monsoon in the State,” IMD Scientist C.S. Patil said. Officials also noted that El Nino delayed the onset of the southwest monsoon in Karnataka, compounding the seasonal deficit.

Why it matters

The four-month southwest monsoon period accounts for the bulk of annual rainfall across Karnataka, recharging reservoirs and groundwater and sustaining agriculture. This season’s underperformance—particularly the 20-year low at the Bengaluru city observatory and double-digit deficits across major subdivisions—sets the stage for tighter water availability and heightened vigilance in the months ahead, even as isolated heavy showers continue to punctuate the post-monsoon transition.