Kolkata: The monsoon arrived in Kolkata and most parts of south Bengal on a cloudy Friday, as the city recorded a maximum temperature of 34 degrees Celsius. While some areas experienced light drizzles, the Met office predicts scanty rainfall in and around the city over the next seven days. This marks the earliest monsoon onset in Kolkata since 2021, when it arrived on June 11. In 2025, the monsoon had reached Kolkata on June 17.
Weak Monsoon Currents
Despite reaching south Bengal, the monsoon currents remain weak. A seasonal trough extending from northwest Rajasthan to the northwest Bay of Bengal may trigger sporadic rain, according to weather scientists at the Regional Meteorological Centre (RMC). RMC scientist Sourish Bandyopadhyay stated, "Barring parts of Purulia, monsoon has covered almost all of Bengal. We expect very light to moderate rain across south Bengal and Kolkata. Wind and thunderstorms will subside, replaced by prolonged drizzles. Cloudy conditions will persist, and temperatures will gradually drop. However, without a strong system, heavy monsoon rain will not occur immediately."
Monsoon Progress and El Niño Impact
Monsoon currents are expected to cover the remaining parts of Bengal by Saturday. This year, the India Meteorological Department (IMD) has forecast El Niño conditions that could hinder rainfall at the start of the monsoon. Meteorologists indicate that most regions, including east and south Bengal, may be affected. This could lead to above-normal maximum temperatures for most of June across large parts of India, including the east, while average monthly rainfall is expected to be below normal.
El Niño occurs when the western Pacific Ocean remains relatively cooler than the east. This causes winds to travel downward, which is not conducive to cloud formation. In contrast, the eastern Pacific, far from the Bay of Bengal, experiences reverse conditions, with hot winds spiraling upward and forming clouds. A weather scientist at the RMC explained, "Since the western Pacific is closer to the Bay of Bengal, where monsoon currents originate, the latter are likely to be weak during the onset. This will not only reduce rain but also lead to more rainless days, pushing temperatures up, especially in June. Thus, we may see weak monsoon currents and infrequent rain after the onset. However, this does not mean the monsoon will be delayed; it is progressing on schedule and could reach east India on time. But that does not guarantee adequate rain due to the El Niño effect."
Potential Consequences
El Niño disrupts moist wind currents, causing the monsoon to be delayed or weaker. This significantly affects seasonal rain that agriculture and local reservoirs depend on. It also triggers intense heatwaves. Instead of continuous rain, east India may experience longer dry spells punctuated by short, heavy bursts of precipitation, increasing the risk of both drought and localized flash flooding. A meteorological scientist warned, "A powerful El Niño is developing in the Pacific Ocean, pushing the country toward a starkly below-normal monsoon. For east India and regions like Kolkata, this condition is expected to make June exceptionally dry, resulting in below-normal average monthly rainfall."
