Factors Behind Monsoon’s Early Nationwide Arrival in 2025

Early Monsoon 2025 Latest News

• The southwest monsoon covered the entire country by June 29, nine days earlier than its usual date of July 8. 
• This is only the tenth time since 1960 that the monsoon achieved nationwide coverage in June.

Early Onset in Kerala Set the Pace

• The monsoon arrived in Kerala on May 24, eight days earlier than usual, driven by an active Madden-Julian Oscillation (MJO) phase in mid-May. 
• This early onset laid the foundation for the monsoon’s rapid progress.
• Monsoon Progress: Mostly Ahead of Schedule
  • South, East, and Northeast India saw early arrival.
  • Northwest India was near normal.
  • Central India witnessed slight delays.

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Key Drivers of the Monsoon’s Rapid Advance

• The southwest monsoon covered the entire country by June 29, nine days ahead of its normal schedule of July 8. 
• This marks only the tenth instance since 1960 that nationwide monsoon coverage occurred in June.

Low Pressure Systems

• India experienced five low-pressure systems in June. 
• These act as moisture magnets, drawing in rain-bearing winds and accelerating monsoon movement inland.

Active Madden-Julian Oscillation (MJO)

• MJO is a moving system of clouds, rainfall, winds, and pressure near the equator that travels eastward. 
• When active near India, it enhances monsoon by increasing cloud cover and moisture, leading to stronger rainfall. 
• An active MJO phase significantly boosts monsoon onset and progression.
• June continued to see an active MJO, enhancing cloud formation and pushing rainfall northwards, aiding monsoon spread.

Favourable Monsoon Trough Position

• The monsoon trough is an elongated low-pressure area extending from northwest India to the Bay of Bengal. 
• It plays a key role in determining rainfall distribution during the monsoon. 
• A favourable monsoon trough position, especially when it shifts south of its normal, helps draw in moisture-laden winds from the oceans, intensifying rainfall over central and northern India. 
• Its position influences the strength, spread, and duration of monsoon rains.
• The monsoon trough remained south of its normal position, facilitating increased moisture inflow and early rainfall across regions.

Neutral ENSO (El Niño-Southern Oscillation) Condition

• ENSO is a climate pattern involving temperature fluctuations in the central and eastern tropical Pacific Ocean, with three phases: El Niño, La Niña, and Neutral.
• A neutral ENSO phase means sea surface temperatures are close to average. 
• This phase neither suppresses nor excessively enhances rainfall, allowing the Indian monsoon to progress normally, supporting stable and widespread rainfall patterns.
• ENSO was in a neutral phase, supporting normal monsoon rainfall.

Neutral IOD (Indian Ocean Dipole) Conditions

• An is a climate phenomenon marked by differences in sea surface temperatures between the western and eastern Indian Ocean. 
• It has positive, negative, and neutral phases.
• A neutral IOD phase means there is little to no temperature difference between the two regions, resulting in minimal influence on the Indian monsoon. 
• This allows monsoon rainfall to be primarily driven by other favorable factors like MJO and ENSO.
• This year, IOD also remained neutral, having minimal impact—neither enhancing nor suppressing rains.

Conclusion

• This year’s monsoon has been marked by early onset, rapid progression, sudden pauses, and localised weather disasters. 
• With much of the season still ahead, it remains uncertain whether the pattern will stabilise or intensify further.

Source: IE | DTE | IE