Monsoon Delay in Kerala: Why IMD Has Repeatedly Changed the Onset Date This Year

Thiruvananthapuram: After initially forecasting an early arrival of the Southwest Monsoon over Kerala around May 27, the India Meteorological Department (IMD) has been forced to repeatedly revise its projections, with the official onset now expected only after June 5–6. The delay has raised questions about why forecasting the monsoon has become increasingly difficult and why onset dates are changing more frequently than in the past.  The Southwest Monsoon normally arrives over Kerala around June 1 and serves as the gateway for the rainy season across the entire country. Its arrival is crucial because nearly 70 percent of India’s annual rainfall is received during the monsoon season, making it the backbone of agriculture, water security, and rural livelihoods.  This year, weather conditions initially appeared highly favorable. The monsoon advanced rapidly over the Andaman and Nicobar region ahead of schedule, prompting IMD to predict an early onset over Kerala. However, the atmosphere failed to maintain the momentum required for a full-fledged monsoon advance, forcing meteorologists to revise their forecasts multiple times.  One of the primary reasons behind the delay has been the absence of the complete set of meteorological conditions required for an official declaration. Contrary to popular belief, rainfall alone is not sufficient for IMD to announce monsoon onset. The department requires widespread rainfall over designated stations, strong and sustained westerly winds in the lower atmosphere, and adequate clouding and convective activity over the region. While Kerala has received intermittent rain, these parameters have not simultaneously reached the required threshold.  Meteorologists have also pointed to the influence of a developing typhoon over the western Pacific Ocean. Such systems can alter large-scale atmospheric circulation and pull moisture away from the Arabian Sea and Bay of Bengal, weakening the monsoon flow toward the Indian coast. At the same time, a cyclonic circulation near the Lakshadweep region has disrupted the normal rainfall distribution pattern, preventing the establishment of sustained monsoon conditions over Kerala.  Another factor has been unfavorable wind patterns. According to IMD officials, the depth and strength of the westerly winds have not been adequate to support monsoon advancement. Outgoing long-wave radiation values, which help indicate cloud formation and convective activity, have also remained less favorable than expected. These atmospheric shortcomings have delayed the official declaration despite the presence of scattered rainfall.  The frequent changes in onset forecasts also reflect a larger challenge emerging in weather science. Climate change is making monsoon behavior increasingly erratic. Rising ocean temperatures, shifting pressure systems, changing wind circulations, and more frequent extreme weather events are creating greater uncertainty in seasonal forecasting. Meteorologists today face a far more dynamic atmosphere than they did two or three decades ago.  Experts note that modern monsoons are no longer following traditional patterns consistently. In some years, the monsoon arrives exceptionally early, as happened in 2025 when it reached Kerala eight days ahead of schedule. In other years, atmospheric disturbances interrupt its progress despite favorable initial conditions. Such fluctuations are becoming more common due to changing global climate systems.  The delay is being closely watched by farmers, policymakers, and economists across the country. While a delay of a few days does not necessarily indicate a weak monsoon season, prolonged uncertainty can affect sowing decisions, water management planning, and agricultural operations. Fortunately, current forecasts suggest that monsoon-supportive winds may strengthen after June 5–6, allowing the system to establish itself over Kerala and resume its northward march across India.  The evolving situation highlights a new reality for India’s weather forecasting system. As climate variability increases, forecasting monsoon onset is becoming less about predicting a fixed date and more about monitoring a complex interaction of oceans, winds, clouds, and global weather systems. The repeated revisions by IMD this year are therefore not necessarily forecasting failures but evidence of how rapidly atmospheric conditions can change in the era of climate uncertainty.  For now, Kerala continues to wait for the official declaration of the monsoon. And as the country watches the skies, the delayed onset serves as another reminder that India’s most important weather phenomenon is becoming increasingly unpredictable in a warming world.