Hailstones the size of a fist fell on Paraguay’s capital Asunción on Saturday 3 October, 2026. The storm also hit nearby cities in the Central department, heavily damaging roofs and vehicles. Paraguay’s Department of Meteorology and Hydrology (DMH) points to extreme heat, humidity and the El Niño climate pattern. With another storm system forecast from Thursday 8 October, Paraguay’s giant hail is making headlines all around the world.
The storm that struck Paraguay on 3 October
The storm arrived in the afternoon and evening of Saturday 3 October. It hit Asunción and the Central department, the ring of cities around the capital.
Hail in the area is usually small, about the size of a little fingernail, according to DMH director Eduardo Mingo. On Saturday the stones reached the size of a fist, he says. That means at least 5 to 7 centimetres, and in some cases 10 to 12, or roughly a hen’s egg to a grapefruit.
How does hail grow so large?
Hail forms inside thunderstorms. Strong updrafts, which are rising currents of air, carry raindrops into extremely cold layers of the atmosphere. There, the drops freeze around a tiny piece of ice. The stone grows layer by layer as it collides with supercooled water, liquid droplets that stay unfrozen below 0 °C.
A stone can fall out of the updraft or be swept back up, repeating the cycle several times. The stronger the updraft, the larger the stone it can hold. The US National Oceanic and Atmospheric Administration (NOAA) puts numbers on this. A hen’s egg-sized stone needs an updraft of roughly 110 kilometres per hour, and a grapefruit-sized one about 160. The biggest stones tend to come from supercells, long-lived storms with a sustained updraft.
Why Paraguay sits in a global hail hotspot
Giant hail in Paraguay is not a freak event. A Nature Geoscience study, led by the European Severe Storms Laboratory, mapped very large hail worldwide from 1950 to 2023. It defines this as stones of 5 centimetres or more. Northern Argentina is the global hotspot, followed by Uruguay, Paraguay, southern Brazil, the US Great Plains and South Africa. One reason, the study notes, is the South American low-level jet, a stream of warm, humid air that feeds storms.
A second study, in Weather and Climate Extremes, analysed conditions favourable for severe storms from 1980 to 2021. It found them most frequent in the Andes foothills in Argentina and at the triple border where Argentina, Brazil and Paraguay meet. At the triple border, they peak in spring.
The long-term trend is not upward, however. Both studies point to fewer favourable conditions in parts of South America, mainly because of drier air. The second study did find a possible spring increase near the triple border, but its authors say it is not statistically significant. A single storm does not reveal a trend.
“Very close to our heads”: Why the storm was so intense
Intense thunderstorms are normal when winter turns to spring. This year, Mingo describes El Niño as an amplifier, adding moisture and heat to systems that would otherwise be ordinary. The heat was already extreme. Mariscal Estigarribia, in the Chaco, Paraguay’s western region, reached 43.8°C in late September 2026, breaking a 74-year record. Together with high humidity, that created storm clouds with severe instability.
Then the freezing level made the difference. Cold air remained high above the city. The 0°C level probably sat low in the atmosphere, “very close to our heads”, Mingo told local media. The stones had little time to melt as they fell.
Whether the 3 October storm was a supercell is not confirmed. Mingo urges caution until technical evaluations finish, including over reports of tornadoes on social media.
Can Paraguay’s giant hail be predicted?
The season is easier to anticipate than the storm. In August, The Asunción Times reported that forecasters expected El Niño to bring stronger winds and heavier hail. Day to day, the DMH issues special bulletins when storms approach, and these always include possible hail. A bulletin issued on Friday 2 October, a day before the storm, covered all 17 departments, as Paraguay’s regions are called. It warned of frequent storms, gusts of around 100 kilometres per hour and localised hail.
Forecasting the size of the stones is far more difficult. Storm clouds contain ice by nature, but predicting how large the hail will grow is very difficult, Mingo acknowledges. Hail is also highly local. Munich Re, a reinsurer and partner in the Nature Geoscience study, notes that hailstorms usually affect only small areas.
What comes next?
According to the DMH, another storm system could affect much of the country from Thursday 8 October, with a possibility of severe weather.
The ingredients are the same as before the 3 October storm: hot, humid air with northerly and north-easterly winds, Mingo explains. The system is expected to sweep the Eastern Region, where Asunción lies, in much the same way. Between Thursday afternoon or evening and Friday 9 October, a scenario similar to the 3 October storm could develop.
This does not necessarily mean the same event will repeat. As of 6 October, the impact is the uncertain part, and forecasters are waiting for reports from Argentina, where large hail also fell. Pinpointing where the next storm will strike, and how big its hail will be, remains out of reach. Mingo’s advice is measured: “Do not expect the world to collapse, but be prepared just in case.”
