Karnataka Post-Monsoon Forecast: Rainfall Deficit to Threaten Bengaluru Water Supply

As the monsoon draws to a close, residents across Karnataka are closely monitoring the latest ಹವಾಮಾನ ಮುನ್ಸೂಚನೆ (weather forecast). According to reports from Prajavani, the India Meteorological Department (IMD) indicated that the post-monsoon season was expected to commence around October 16, 2026. However, the outlook remains cautious, as rainfall from October to December is projected to fall below the long-term average of 182.2 mm for the state.

The situation is particularly concerning for Bengaluru. Data reported by Asianet News Kannada reveals the city recorded a significant 43% deficit in monsoon rainfall this year, receiving only 313 mm compared to the required 549 mm. This shortfall has led to critically low water levels in lakes, raising serious alarms regarding borewell water security as the summer months approach.

Why is Karnataka facing a rainfall deficit?

Experts point to global climate patterns as the primary drivers for this suppressed rainfall. As detailed by Vijay Karnataka, strong El Niño conditions in the Pacific Ocean, coupled with a neutral Indian Ocean Dipole (IOD), are the main factors preventing the expected showers over the region.

• El Niño: Sea surface temperatures in the Pacific are higher than average and expected to remain strong until the end of the year.
• Neutral IOD: The Indian Ocean Dipole is currently neutral, failing to provide the moisture boost needed for heavy rains.
• Temperature Rise: Projections suggest that both daytime and nighttime maximums will be higher than usual across Karnataka during this period.

Impact on Water and Agriculture

The predicted deficit poses a direct challenge to both urban infrastructure and rural livelihoods. With the post-monsoon rains expected to be below-normal, farmers are urged to prioritize water conservation and consider alternative crop planning to mitigate the risk of crop failure.

Metric	Average/Required	Actual/Projected
Karnataka Rainfall (Oct-Dec)	182.2 mm	Below Average
Bengaluru Monsoon Rainfall	549 mm	313 mm (43% Deficit)
Expected Onset Date	-	October 16, 2026

While forecasts are probabilistic, local mitigation efforts and unexpected weather events could still alter the outcome. For now, the focus remains on managing existing water reserves to ensure the state survives through the dry season.