Just How Dry Was It?
The numbers from the India Meteorological Department (IMD) are stark. The city’s main observatory recorded only 23 mm of rainfall for the entire month of July. This is a dramatic drop from the typical average of 80 mm to 100 mm for the month. The only July drier
than this one was all the way back in 1918, when a mere 18.5 mm of rain was recorded. To make matters more unusual, this dry spell was paired with record-breaking heat. On July 14, Bengaluru registered its hottest July day in 112 years, with the temperature hitting 33.6°C. This combination of a severe rain deficit and abnormal heat made for an exceptionally strange weather month in a city famed for its pleasant climate.
Why Did the Monsoon Fail the City?
Meteorologists point to a confluence of weak weather systems. The primary driver of monsoon rain in the region is a strong, moist westerly wind flow from the Arabian Sea. This July, that flow was significantly subdued. An offshore trough, a zone of low pressure that typically runs along the west coast from Gujarat to Kerala and helps pull moisture inland, was also weak and inactive. This meant there was no strong trigger to cause widespread, sustained rainfall over South Interior Karnataka, the region where Bengaluru is located. While some brief showers occurred at the very end of the month, they were not enough to overcome the massive deficit. Forecasters had already predicted a below-normal monsoon for many parts of India, citing factors like a developing El Niño in the Pacific, which tends to suppress monsoon rainfall.
The Urban Effect: Is the City Making Itself Warmer?
While large-scale atmospheric patterns dictate the monsoon, Bengaluru's own rapid urbanisation plays a significant role in modifying its local climate. The phenomenon known as the "Urban Heat Island" (UHI) effect is well-documented in the city. Decades of unplanned growth have seen a dramatic loss of green cover and water bodies, which have been replaced by concrete, asphalt, and other surfaces that absorb and retain heat. Studies show a massive 1055% increase in built-up areas between 1973 and 2023, while vegetation cover plummeted by 88%. This transformation leads to higher land surface temperatures. While not a direct cause of a failed monsoon, a hotter, drier urban environment can alter local weather patterns, influencing how and where rain falls and exacerbating the discomfort from a dry spell.
Immediate Consequences and Future Outlook
The poor July rainfall has raised concerns across Karnataka, which was already facing a 26% monsoon deficit by the end of the month. For Bengaluru, a dry July puts pressure on water resources. The city's water supply is heavily dependent on the Cauvery basin and local reservoirs, which rely on monsoon rains for replenishment. In early July, anticipating a weak monsoon, the Bengaluru Water Supply and Sewerage Board (BWSSB) had already announced restrictions, banning the use of drinking water for non-essential purposes like washing cars and filling pools. Luckily, robust pre-monsoon showers earlier in the year meant the city's annual rainfall total remains within the normal range for now. However, that surplus has been steadily eroded. The IMD expects rainfall activity to potentially revive briefly in mid-August but remain weak for much of the month, meaning the city is not out of the woods yet.
