An extratropical cyclone is keeping southern Brazil on alert for extreme rain this week, days after a hailstorm affected 9,517 people and damaged about 2,200 homes in Rio Grande do Sul, Brazil's southernmost state. The state Civil Defense released the tally on Sunday (27); it records no deaths or missing persons.

Santiago, in the state's central region, was the hardest hit municipality, with 5,000 residents affected and about 1,000 properties damaged. On Saturday (26), hail fell in such volume that it covered the city's streets in white. In Alegrete, on the western border, 2,000 people were affected and 700 homes damaged, while Capão do Cipó and Catuípe recorded 820 and 800 people affected, according to Folha de S.Paulo. The storm entered the state through the western border on Saturday afternoon, with hail in Barra do Quaraí and a severe storm in Uruguaiana early in the evening. Outlets diverge on injuries: Folha reported one person injured, ten left homeless and twenty displaced, all in Alegrete; G1, citing the same agency tally, said no one was injured.

Up to 300 mm of rain and risk of new floods

The concern now is the days ahead. According to Folha, a low-pressure area between northern Argentina and Paraguay is pushing warm, moist air toward Rio Grande do Sul, and Inmet, Brazil's national weather institute, along with private forecaster Climatempo and the Civil Defense, has kept alerts in place since Friday (25). MetSul Meteorology projects 100 mm to 200 mm of rain through the end of Tuesday (29) in a band running from the west to the highlands, with 200 mm to 300 mm possible in some municipalities; news portal iG cited a risk of up to 270 mm. On Wednesday (30), a cyclone over the Atlantic is expected to push in dry, cold air and drive the instability away. MetSul lists the basins of greatest concern, including the Ibirapuitã, Santa Maria, Vacacaí, Ibicuí, Jacuí, Taquari, Caí, Sinos and Gravataí rivers. The firm notes that in the storm wave of September 21, which left six dead in the state, four victims died from excess rain in the Serra Gaúcha highlands.

What authorities are doing

The Rio Grande do Sul Civil Defense warned of large hail and gusts above 90 km/h in the Campanha plains and in the western, Missões, northwestern, northern and central regions. On Sunday night, alert notices remained active on the agency's website. According to Diário Gaúcho, the state has already sent 30 high-risk emergency alerts to mobile phones this year via cell broadcast, three times more than in all of last year. In Santiago, residents lined up to collect tarps, and the Civil Defense asked them not to climb onto roofs for repairs. In Porto Alegre, the state capital, the municipal Civil Defense asked the regional electoral court to remove wind banners, the cloth panels used in campaign advertising, until Tuesday because of forecast winds of up to 70 km/h that could cause accidents.

The picture repeats an unusual spring. An exceptionally warm air mass over the center of the continent, with highs of 40°C to 45°C in Brazil's Center-West and Southeast, is feeding the storm clouds over the South, according to MetSul, which links the pattern to a record-strength El Niño in the Pacific. Inmet forecasts above-average rain in the South and Southeast in October.