MAY Pre Monsoon Rainfall : 2025 & 2026
Pune: 240.2 mms ( 30 mms) Record for May beating 182 mm in 1933
2026 May = 107 mm
Mahabaleshwar: 445 mms ( 67 mms)
2026= 7.2 mm
Panjim: 637mms ( 65 mms)
2026 = 62 mms
Cherrapunji : 1437
2026= 620 mm (May)
The South Asian Monsoon rainfall season is all set to make its first northward progression and onset over the Indian subcontinent and the neighbouring regions starting from the first week of June 2026. Latest available forecast guidance based on several global numerical weather prediction models indicate the likelihood of the beginning of the rainy season in a few days from now. Conditions are favourable for monsoon onset over Kerala between 3 and 5 June, and further progression along the west coast up to Konkan, parts of east and North East India to gradually set in during the first two weeks of June. Large scale environmental conditions and indicators of Monsoon rainfall including significant inter hemispheric pressure gradient, stronger upper level easterlies , strong low level westerlies, deeper moist column/moist adiabatic temp. profile etc., are all expected to establish during the first fortnight. Meanwhile, parts of northwest, west and adjoining central India can come under the influence of a southward digging deepening upper level trough in the subtropical westerlies. (Those rains not to be confused as Monsoon rainfall).
Scientific diagnostic reasoning:
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Large scale circulation analyses and forecasts on intraseasonal time scales suggest that the aforementioned monsoon's first northward progression is likely associated with an evolving equatorial wave mode that is expected to constructively interfere with the background climatological monsoon circulation as it propagates poleward. As it does so, the background conditions are also all expected to evolve quite quickly like the stronger reversal of meridional temp. gradient, northward receding of the upper level subtropical jet stream, intensification of the southern hemispheric Mascarene subtropical High, deepening heat low and the Monsoon Trough etc.,
Check the earliest 40° and 50° records as available with Vagaries on Vagaries Extreme Blog
Read our Views on Author's Page
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https://youtube.com/shorts/OBiZUsdu3Ig?si=I15htrSCur8n1hmk
Monsoon Watch-- 5...29th May 2026
🟢 Vagaries Summary – Monsoon Watch 5
🟢 Pre-Monsoon Rainfall: Near Normal
🟢 May Heat: Near Normal and adequate for seasonal low development
🟢 Equatorial Winds: Strong and supportive for Monsoon progress
🟡 Pressure Gradient: Neutral, but expected to improve further during early June
🟡 IOD: Currently Neutral; possibility of turning Positive later, which could aid the Monsoon
🟢 ENSO: Still Neutral. A fully qualified El Niño is unlikely before August. Any significant impact of a stronger El Niño on India is more likely after September 2026.
🌧️ Overall Assessment: Current indicators remain broadly supportive of normal Monsoon onset and advancement across India.
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Detailed Note:👇
Monsoon Limit Today:
1.El Niño: characterized by a positive RONI greater than or equal to +0.5ºC.
The most recent RONI value (February/Mar/April 2026) is -0.5ºC.
By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons.
ENSO Alert System Status: El Niño Watch ENSO-neutral conditions are present.
* Equatorial sea surface temperatures (SSTs) are near-to-above-average across the central and eastern Pacific Ocean.
El Niño is likely to emerge soon (82% chance in May-July 2026) and continue through Northern Hemisphere winter 2026-27 (96% chance in December 2026 – February 2027).*
So, Effectively, the feared "strong Historical EL Nino" could affect India after September 2026.
2. I.O.D
3.Pre Monsoon Rainfall: Normal
7.Vagaries' Estimate:
Dates of Onset up to Maharashtra.
Monsoon Onset over Kerala /N.E. States; 2nd June-4th June
Coastal Kar: 6th/7th June.
South Konkan/Goa: 8th/9th June
Monsoon Onset over Mumbai/Pune/ West Bengal: 12th/14th June...Pre Monsoon Showers 3rd June onwards.
South Interior Maharastra: 12th June.
North Interior Maharashtra /Marathwada: 15th/18th June.
{Surat/Bharuch/Valsad/Ahmedabad/Baroda: Light to moderate pre monsoon Showers/Thundershowers on 2nd/3rd/4th June. Monsoon after 16th/17th June in South Gujarat.}
