Early Onset of Southwest Monsoon in India 2025

Introduction

The Southwest Monsoon is the lifeblood of India’s climate and economy, delivering nearly 75% of the country’s annual rainfall between June and September. This seasonal wind system is crucial for agriculture, water resources, and the overall socio-economic fabric of the nation. In 2025, India witnessed an unusually early onset of the Southwest Monsoon, raising hopes and questions about its causes, potential impacts, and what the rest of the season might hold.

The Early Onset of Southwest Monsoon in India 2025, examining the meteorological triggers, the regions affected, and the implications for agriculture, the economy, and the environment. We also review the latest IMD forecast 2025, expert insights, and the possible influence of climate change and monsoon variability.

The Southwest Monsoon is a complex weather phenomenon driven by differential heating of land and sea, resulting in moisture-laden winds from the Indian Ocean sweeping across the subcontinent. Its timely arrival is vital for:

• Agriculture: Nearly 42% of India’s workforce depends on agriculture, which is predominantly rain-fed.
• Water Security: Monsoon rains replenish reservoirs essential for drinking water and hydroelectric power.
• Economic Stability: Agriculture contributes about 18% to India’s GDP, and monsoon performance directly affects inflation, rural income, and food security.

Actual Dates of Onset vs. Normal Schedule

• Normal Onset: The Southwest Monsoon typically arrives over Kerala around June 1 and advances northwards, covering most of India by mid-July.
• 2025 Early Onset:
  • Kerala: The IMD officially declared the monsoon onset over Kerala on May 24, 2025—eight days ahead of the usual date.
  • Mumbai: The monsoon reached Mumbai by May 26, 2025, the earliest on record for the city.
  • Other Regions: The monsoon swept rapidly across Tamil Nadu, Karnataka, and Maharashtra, advancing 16 days ahead of the normal schedule in some areas.

Regions Affected Early

• Southern states like Kerala, Tamil Nadu, Karnataka, and Maharashtra experienced early and intense rainfall.
• Major cities including Mumbai and Bengaluru saw monsoon conditions well before their typical onset dates.

Meteorological Reasons

The early onset of the Southwest Monsoon in 2025 was the result of a unique interplay of atmospheric and oceanic factors:

1. Favourable Madden-Julian Oscillation (MJO)

• The MJO is a moving band of clouds, rainfall, and wind that travels eastward around the equator.
• In May 2025, the MJO was in a phase that encouraged convection and rainfall over southern India, accelerating monsoon onset.

2. Sea Surface Temperatures and Atmospheric Moisture

• Higher-than-normal sea surface temperatures in the Arabian Sea and Bay of Bengal increased atmospheric moisture, fueling early cloud formation and rainfall.
• Global warming has led to a 6–8% increase in atmospheric moisture per degree Celsius rise, amplifying the effect.

3. Strong Somali Jet and Cross-Equatorial Flow

• The Somali Jet, a low-level wind stream from the southwest Indian Ocean, was unusually strong in May 2025, transporting significant moisture to India’s west coast.

4. Neutral ENSO and Indian Ocean Dipole (IOD)

• The El Niño–Southern Oscillation (ENSO) was in a neutral phase, removing a common barrier to strong monsoon activity.
• The IOD was also neutral, with forecasts suggesting a possible positive phase later in the season, which could further enhance rainfall.

5. Reduced Eurasian and Himalayan Snow Cover

• Lower snow cover led to increased land heating, strengthening the monsoon circulation4.

Insights from IMD and Scientific Bodies

• The IMD had forecasted a 59% chance of above-normal rainfall for the 2025 monsoon, with an onset date of May 27—five days ahead of normal.
• The department dismissed concerns about El Niño, instead predicting robust monsoon performance.

Benefits for Farmers

• Early Sowing: The early rains allowed farmers in southern and western India to begin sowing kharif crops ahead of schedule, potentially extending the growing season.
• Groundwater Recharge: Early and widespread rainfall helped replenish groundwater and reservoirs, crucial for irrigation and drinking water supplies.

Challenges for Agriculture

• Crop Damage: Intense early rainfall led to waterlogging and soil erosion in several regions, damaging standing crops like onions and jowar in Maharashtra.
• Supply Chain Disruption: Excess moisture threatened stored produce, particularly onions, increasing the risk of spoilage and price spikes.
• Input Planning: Farmers faced difficulties in synchronizing fertilizer and seed application with unpredictable rain patterns.

Economic Implications

• Inflation Risks: Disruptions in vegetable supply chains and crop damage led to rising prices, especially for onions and tomatoes, threatening recent gains in inflation control.
• Rural Income: While a good monsoon generally boosts rural incomes, localized crop losses can offset these gains in affected areas.
• Sectoral Impact: FMCG companies saw a dip in summer product sales due to early rains, while non-perishable sectors like construction experienced only postponed demand.

Urban and Environmental Effects

Changes in Weather Patterns

• Reduced Heatwaves: Early rains brought relief from extreme summer heat, lowering the risk of heatwaves in major cities.
• Flood Risk: The rapid and intense onset increased the risk of urban flooding, especially in cities like Mumbai, which issued red alerts for heavy rainfall.
• Infrastructure Strain: Sudden heavy downpours tested urban drainage systems, leading to waterlogging and traffic disruptions.

Environmental Considerations

• Ecosystem Recharge: Early monsoon rains benefited wetlands and forested areas, supporting biodiversity.
• Climate Variability: The unusual timing and intensity of the monsoon highlighted the growing influence of climate change on India’s weather patterns.

Monsoon Performance Prediction

• The IMD predicts above-normal cumulative rainfall for the 2025 monsoon season, with total precipitation likely to reach 105–106% of the long-period average (LPA).
• For June, rainfall is expected to exceed 108% of the national average.

IMD’s Long-Range Forecast and Expert Views

• The IMD anticipates a temporary pause in the monsoon’s northward advance after the initial surge, a common pattern in recent years.
• Experts caution that while early onset is promising, it does not guarantee a surplus season—breaks in rainfall and regional variability remain possible.
• A slight positive IOD phase developing later in the season could support continued good rainfall in August and September.

Conclusion

The Early Onset of Southwest Monsoon in India 2025 is a striking reminder of the dynamic nature of India’s climate system. While early rains bring hope for robust agricultural output and water security, they also pose challenges in the form of crop damage, supply chain disruptions, and urban flooding. The 2025 event underscores the necessity for early preparedness, adaptive agricultural practices, and resilient infrastructure.

As climate change continues to alter traditional weather patterns, understanding and responding proactively to monsoon variability will be crucial for India’s future. The lessons from 2025 highlight the importance of robust forecasting, scientific research, and policy support to safeguard the nation’s food security and economic stability.

The Indian monsoon is a seasonal reversal of winds, bringing most of the country’s annual rainfall, crucial for agriculture and water resources.

• Types:
  • Southwest Monsoon (June–Sept): Brings ~75% of annual rainfall, affects most of India, arrives in Kerala around June 1.
  • Northeast Monsoon (Oct–Dec): Mainly affects SE coast (Tamil Nadu), brings post-monsoon rains.
• Mechanism: Caused by differential heating of land and sea, shift of ITCZ, Coriolis effect, and influence of jet streams.
• Features: Highly seasonal, regional variation in rainfall, onset and retreat vary each year, prone to breaks and variability.
• Importance: Vital for agriculture (over 50% rain-fed), water supply, hydroelectricity, and rural economy.
• Challenges: Unpredictable onset/withdrawal, floods, droughts, urban flooding, and increasing variability due to climate change.
• Key Factors Influencing Monsoon: El Niño/La Niña, Indian Ocean Dipole, Himalayas, climate change.

Quick Revision:

Aspect	Southwest Monsoon	Northeast Monsoon
Season	June–September	October–December
Direction	Sea to land (SW)	Land to sea (NE)
Main Rainfall Areas	Most of India	SE coast (Tamil Nadu, Andhra)
Key Cause	Low pressure over NW India	High pressure over Asia

Source: IMD, Economic Times, India Today, NDTV Profit, USDA FAS