IMD Monsoon Forecast 2026: Southwest Monsoon Likely To Reach India Early, Kerala Onset Expected On 26 May

India could witness an early start to the 2026 southwest monsoon season, with the India Meteorological Department (IMD) forecasting the monsoon onset over Kerala on 26 May, nearly a week ahead of the normal date of 1 June. The development is significant because the arrival of the monsoon in Kerala officially marks the beginning of the rainy season across the Indian mainland.

The southwest monsoon is crucial for India's agriculture, water supply, power generation and overall economy. After entering Kerala, the monsoon gradually advances towards central, eastern and northern parts of the country over the following weeks, bringing widespread rainfall and relief from intense summer heat.

Early Monsoon May Bring Faster Relief From Heatwave Conditions

Large parts of India have been experiencing high temperatures during the ongoing summer season. An earlier-than-normal monsoon onset could bring quicker relief to several regions, especially southern and central India, where temperatures typically begin easing as rain-bearing winds advance inland.

The IMD said the forecast carries a model error margin of plus or minus four days. Southwest monsoon onset over Kerala normally takes place on 1 June with a standard deviation of around seven days.

IMD Uses Six Weather Indicators To Predict Monsoon Arrival

According to the Ministry of Earth Sciences, the forecast has been generated using an indigenously developed statistical model that has been operational since 2005. The model studies six important atmospheric and climatic indicators before issuing the onset prediction.

These include minimum temperatures over northwest India, pre-monsoon rainfall activity over the southern peninsula, outgoing long wave radiation patterns over the South China Sea and southwest Pacific region, along with lower tropospheric wind conditions over the southeast Indian Ocean and northeast Indian Ocean.

Forecast Accuracy Remained Strong In Recent Years

The weather department said its operational forecasts for monsoon onset over Kerala have remained accurate in most years since 2005, with 2015 being the only major exception.

Recent forecasts have also remained close to the actual onset dates. In 2025, the monsoon arrived on 24 May while the forecast had predicted 27 May. In 2024, the actual onset date was 30 May against a forecast of 31 May. In 2022, the onset took place on 29 May while the prediction was 27 May.

Monsoon Progress To Be Closely Watched Across India

The arrival and spread of the southwest monsoon is one of the most closely monitored weather developments in India every year. A good monsoon season is considered essential for kharif crops, reservoir levels and rural economic activity across the country.

With the IMD now forecasting an early onset, attention will shift towards how quickly the monsoon advances beyond Kerala and whether rainfall activity remains consistent across major agricultural states in the coming weeks.