Argentina on Storm Alert: Cyclogenesis Brings Hail, Up to 100 mm of Rain and Gales Through Tuesday
Argentina · Weather
Key Facts
—The event. A cyclogenesis is unfolding over Argentina from Sunday 27 to Tuesday 29 September, bringing at least 72 hours of marked instability across most of the country.
—Sunday. Hail fell in parts of Buenos Aires province as the national weather service (SMN) issued yellow and orange storm alerts; the orange tier carried 50–90 mm of rain and gusts that could top 100 km/h.
—Monday. The widest coverage: rain and storms could reach more than 65% of the country, focused on La Pampa, Córdoba, Santa Fe, Entre Ríos and Buenos Aires before spreading to Cuyo and the north.
—Accumulations. The ECMWF model projects 50–100 mm across parts of Buenos Aires, Córdoba, Santa Fe, Entre Ríos and the central Litoral, with localised totals above 100 mm.
—Coast and mountains. Atlantic-facing Buenos Aires expects gusts of 70–75 km/h and waves over two metres, while late snowfalls of up to 25 cm are forecast for the Cuyo and northern Andes on Monday.
Latest — September 28, 2026, morning local time (Córdoba hailstorm)
— Córdoba struck before dawn: severe thunderstorms with heavy hail hit Córdoba province from around 5 a.m. on Monday, first in the northern districts of the provincial capital, then across the Sierras Chicas; Unquillo and Mendiolaza were the hardest-hit towns (El Doce).
— Damage reported: in Unquillo the hailstorm destroyed the Paseo de los Artesanos, toppled signs and cut power; stones the size of an orange were photographed in Córdoba, and dry hail battered the Ruta 5 toll station between Alta Gracia and the capital, with Villa Carlos Paz also in the storm corridor (Cadena 3).
— Sharp cooling: meteorologist Marcelo Madelón expects intense showers, southerly winds and a high of only 23–24 °C on Monday, after 34.6 °C on Sunday; the clash of near-45 °C air in the north with cooler, humid air — plus extra El Niño moisture — is feeding the storms.
— Alert area: the warning covers Córdoba, Santa Fe, Entre Ríos, Buenos Aires, La Pampa, San Luis, Mendoza, Tucumán, Santiago del Estero and Corrientes, with further storms expected through Tuesday.
Argentina is closing September under a nationwide storm pattern: a slow-forming cyclogenesis has already dropped hail on Buenos Aires province and is set to expand on Monday, with the capital region facing gales and downpours through Tuesday.
What a Cyclogenesis Is — and Why It Hits Now
Cyclogenesis is the formation or deepening of a low-pressure centre in the atmosphere. In plain terms, it forces air masses of different temperatures and characteristics together — and that contrast builds extensive cloud, storms, heavy rain and intense wind.
“The most relevant feature of the weekend will be the start of a very slow cyclogenesis process, which begins on Sunday and only peaks on Tuesday,” meteorologist Cindy Fernández told Meteored. The system follows several days of unusually high temperatures and dry, clear skies across the centre and north — exactly the contrast that feeds strong storms.
The mature branch of the low will concentrate the heaviest rain and storms over Uruguay, southern Brazil and Argentina’s Litoral, while also reaching the south-east of Buenos Aires province, where coastal sectors face wind and rain of near-temporal intensity, Infobae reported.
Sunday: Hail in Buenos Aires, Orange and Yellow Alerts
The first storms on Sunday concentrated on eastern Entre Ríos and northern Uruguay before advancing across Entre Ríos, north-western Buenos Aires, south-eastern Santa Fe, southern Córdoba and La Pampa, with short bursts of rain, frequent lightning, possible hail and intense gusts. Initial accumulations were forecast at 20–50 mm, locally higher.
Hail did fall in Buenos Aires province during the day, Canal 26 reported, showing streets covered in hailstones in several districts. The SMN stacked alerts through the day: yellow warnings for storms with 20–50 mm of rain, and an orange warning for stronger storms with 50–90 mm, hail of various sizes and gusts that could exceed 100 km/h, according to TN.
The yellow alert for storms remained in force for Monday 28 September, La Nación reported, with the warning window extending into the early hours of the new week.
Monday Brings the Widest Coverage
Monday is set to be the day of greatest territorial extent: rain and storms could cover more than 65% of Argentina, centred on La Pampa, Córdoba, Santa Fe, Entre Ríos and Buenos Aires province. The instability then spreads to Cuyo and much of the north as the cold front advances, with storms potentially carrying strong gusts, abundant rain in short periods and hail.
The Buenos Aires Metropolitan Area (AMBA) faces a stretch of changeable weather from Sunday to Tuesday: showers and isolated storms of irregular intensity, with occasional stronger events. The cyclogenesis influence becomes most visible on Tuesday, when the low-pressure centre sits over Uruguay — at that point, south-westerly gusts could exceed 60 km/h in the AMBA, according to Meteored projections cited by Infobae.
The ECMWF model places the largest accumulations — between 50 and 100 mm, locally more — in parts of Buenos Aires, Córdoba, Santa Fe, Entre Ríos and the central Litoral. Forecasters caution that the reach and intensity of individual storms may shift as the system evolves, making it necessary to follow the SMN’s official alerts.
The Coast, Patagonia and the Andes
On the Buenos Aires Atlantic coast, south-easterly gusts of 70–75 km/h are expected alongside a rising sea and waves that could top two metres — a combination of wind, surf and sustained rain that can cause coastal flooding, urban waterlogging and difficult driving conditions in the worst-hit sectors.
Patagonia is already unstable from Pacific systems: alerts for persistent rain were reactivated on Saturday for the Río Negro cordillera and southern Neuquén, with up to 30 mm expected and more possible locally. The warning carries weight because the zone was under red alert during the week, with road cuts, flooded settlements and swollen rivers. Late-season snow of up to 25 cm is forecast for Monday in the cordillera of Mendoza, San Juan, northern Neuquén, La Rioja and Catamarca.
The system should start moving away to the south-east over the Argentine Sea after Tuesday 29, though cloud will persist over much of the country and rain will continue over Córdoba and the north-west.
What We Could Not Confirm
At the time of writing, the SMN and provincial civil defence agencies had not published consolidated damage or evacuation figures for Sunday’s storms, so we cannot give verified totals beyond the confirmed hail reports and the alert parameters. Whether classes will be suspended in any province on Monday had not been confirmed. The exact peak strength and track of the low on Tuesday remain model projections — the ECMWF-based estimates cited here could shift, and localised maxima may differ from regional averages.
More: Argentina news in English, every day from The Rio Times.
Frequently Asked Questions
What is the cyclogenesis hitting Argentina?
It is the slow formation of a low-pressure centre over the region between Sunday 27 and Tuesday 29 September. The clash of warm and cold air masses is producing storms, heavy rain, hail and strong winds across most of the country, with the peak expected on Tuesday.
Will Buenos Aires be affected by the storms?
Yes. The province saw hail on Sunday under yellow and orange SMN alerts. The metropolitan area (AMBA) faces showers and isolated storms through Tuesday, when south-westerly gusts could exceed 60 km/h as the low-pressure centre sits over Uruguay.
How much rain is forecast in Argentina this week?
The ECMWF model projects 50–100 mm in parts of Buenos Aires, Córdoba, Santa Fe, Entre Ríos and the central Litoral, with localised totals above 100 mm. Sunday’s initial storms were forecast to drop 20–50 mm, locally more.
Is snow expected in Argentina during this event?
Yes. Late-season snowfalls of up to 25 cm are forecast for Monday in the Andean cordillera of Mendoza, San Juan, northern Neuquén, La Rioja and Catamarca, while Patagonia’s Río Negro cordillera and southern Neuquén remain under rain alerts.
Connected Coverage
The same late-September instability is battering the other side of the Andes — Chile is under its own storm alerts this weekend.
Chile on Storm Alert: Thunderstorm Warning for the South Today as Another Atmospheric River Looms
Sources: Infobae; TN; La Nación; Canal 26; Meteored.
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