Weekend Storm Risk Returns to Centre‑South Brazil

Overview

• As of Friday, Sept. 18, national and regional forecasts show the Centre‑South shifting from a short dry spell back to instability as increased moisture transport and lower pressure set the stage for weekend storms.
• Inmet has issued an orange alert for Vale do Ribeira covering Registro, Eldorado, Sete Barras and Iguape with forecasts of 50–100 mm per day, winds of 60–100 km/h and possible hail.
• Defesa Civil warned of strong rain and flood risk for Porto Alegre and its metro area from Saturday into Monday and urged people to avoid slopes, rivers and flood‑prone streets.
• Mato Grosso do Sul will swing from near‑40°C heat on Friday to a transition day on Saturday with thunderstorms that may produce heavy rain, lightning, wind gusts of 50–70 km/h and possible hail by the weekend.
• A cold air mass keeps the South unusually cool with frost potential while large areas of the North and Centre‑West face extreme heat and very low humidity, a contrast that raises both flood and health/fire risks for different communities.