MAY Pre Monsoon Rainfall : 2025 & 2026
Pune: 240.2 mms ( 30 mms) Record for May beating 182 mm in 1933
2026 May = 13 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.}
Hype created and News Circulation by Foreign Agencies about Alleged "Indian Heat Waves"
24th May..
Mumbai
Hot Night : The 4th hottest (May Month) night Temperature ever recorded at 29.9°c on 24th morning.
Compared with the Hottest ever first three nights for May. 
🌩️ Pune Thunderstorm Update – 🌧️
Strong post-noon thunderstorm activity lashed several parts of Pune district on 22nd May, bringing intense localised rainfall and gusty conditions.
📍 Pune Rainfall (mm) till 8.30 IST – 23 -05-2026
Nigdi 97
CHINCHWAD 67
Kondwa 58
ZP School Pisoli 56
DUDULGAON 38.5
SHIRUR 35.5
Aundh 35
KURVANDE 32.5
NDA 30.0
AMBEGAON 28.0
RAJGURUNAGAR 27.0
NIMGIRI 23.0
Bhosale Nagar 22
NARAYANGOAN 21.5
BALLALWADI 21.5
PASHAN_AWS 18.5
SHIVAJINAGAR 13.3
KOREGAON PARK 10.0
LAVALE 8.5
HAVELI 1.5
GIRIVAN 0.5
in mms
⚡ Heavy convective clouds developed rapidly during the afternoon due to increasing moisture incursion and intense daytime heating over interior Maharashtra.
🌦️ More localised thunderstorms are possible over Pune district and nearby Ghat regions during the next 2–3 days.
🌐 Details & Updates: www.vagaries.in
#P#Punerains
Weather Watch Summary 22nd May - 30th May.
1. There seems a probability of a Low forming in Central Arabian sea on 23rd.
2. This may pull off the moisture from the West Coast.
3. Rainfall in patches likely on West Coast and Thundershowers in Ghats till May end.
4. That is till the AS 1 moves away.
5. South West Monsoon expected in Kerala around previous expected date 30th May - 1st June.
6. Mumbai can get pre- monsoon thundershowers after 1st/2nd June.
7. If progress is maintained, Monsoon can arrive in Mumbai around 11th June.
8. Remainder of May: Mumbai:
Normal humid weather around 34°/35°.
A few patchy localised ( Hit and Miss type) showers on the odd day. Evenings.
9. Pune: Partly Cloudy by afternoon with localised thundershower. Around 40°
10. Vidarbha will be the normal hotbed at 44°- 47°.
20th May
Possible chance of Derailing the El Niño effect this summer:
A Positive I.O.D. can partially offset weak El Niño effects and sometimes supports a near-normal Indian Monsoon.
A Positive I.O.D. occurs when the western Indian Ocean becomes warmer than normal, while the eastern Indian Ocean near Indonesia turns cooler than normal.
This temperature contrast strengthens winds towards Africa and often helps enhance the Indian Monsoon by increasing moisture flow towards India.
Typical Effects:
Better monsoon support for India 🌧️
Increased rainfall over East Africa
Reduced rainfall near Indonesia/Australia
The Indian Ocean Dipole (IOD) is currently in a neutral phase, hovering around -0.04.
Forecasts project a shift to a positive IOD phase by late June or July 2026, with the index potentially exceeding the +0.5 threshold as a developing El Niño influences the broader climate system.
This may counter the developing El Nino. Indian Ocean may start working a bit in India’s favour even as the Pacific turns hostile.
Still Too early to make a call
18th May Post
Highlight: Pre Monsoon Low in Arabian Sea precipitates heavy rains in Kerala and Coastal Karnatak upto Goa.
Kozhikode 101 mm
Kannur 88 mm
Cochin 54 mm
Gadag 84 mm ( Kar)
Mangalore 14 mm(Kar)
Goa Margao 47 mm
Goa panjim 11 mm
This Low will, later in the week, mildly activate the Off shore West Coast Trough.
Hence some pre monsoon thundershowers can be expected Along entire West Coast from 24th May - 28th May.
Konkan ( Mumbai) can expect showers from 24th - 28th May.
Monsoon Watch - 4... Summery 👉
16th May
1. ENSO Status
Current ENSO conditions remain Neutral.
Latest model guidance indicates that El Niño conditions may begin evolving after July, with a more noticeable strengthening likely after September.
The present indications suggest that ENSO is not expected to significantly interfere with the initial onset phase of the South-West Monsoon.
A noticeable South-Westerly turn is visible off the Somalia coast, with Sea Surface Temperatures (SSTs) there around 24°C, supporting gradual strengthening of the low-level jet.
The Seasonal Low over the core Thar region is currently around 998 mb, which is considered satisfactory for this stage of May.
Formation is progressing well despite temperatures remaining broadly within the normal range.
However, the pressure gradient still needs further strengthening during the coming 10–12 days.
The South-West Monsoon has entered the Andaman Sea, marking the formal beginning of monsoon advancement across the eastern sector.
Arabian Sea branch parameters are also progressing steadily and favorably.
Increasing heat across Central and Northwest India, with temperatures expected to cross 45°C more frequently, should help strengthen the required monsoon pressure gradient further.
At present trends, the Kerala Monsoon onset is expected around 30th May to 1st June.
The overall monsoon progression presently appears largely on schedule, with both Arabian Sea and Bay branch indicators gradually aligning positively.
While ENSO evolution towards El Niño later in the season remains a factor to monitor carefully, the immediate onset phase currently does not show any major adverse signals.
Rainfall as on 16th Morning in Andamans (Weak Monsoon Advance)
Carnicobar 44mms
Mayabandar 14 mms
Nancowrie 12 mms
Port Blair 5 mms
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15th Night Post
South West Monsoon Announcement # 3
South West Monsoon Advances into South Andaman Islands as a weak current..15th May.
Bulletin of Thai Met Dept.
"The southwest monsoon prevails over the Andaman Sea and the South with more rain and isolated heavy rain in the upper country, while isolated very heavy rain is likely in the North, the Central, and the East."
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13 May observed wind speed during squall and observed lightning strikes
Meerut saw a whopping strike of 519 in 1hr
Unnao massive 952 strikes in 1hr
Raebareilly 655 lightning strikes in 1hr
Observed windspeed in UP on 13may
Monsoon Watch - 4 on blog tomorrow 16th
Southwest Monsoon Announcement # 2
The South-West Monsoon will advance in the Andamans Region by 16th May.
Subject: Heavy to very heavy rains in Thailand,
Strong Wind-Waves in the upper Andaman Sea
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The active low-pressure cell in lower Bay of Bengal will move to the upper Bay of Bengal while the southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf will strengthen."
Meanwhile ,
