Brazil weather: heavy rain, storm alerts for Oct. 21

Brazil's national weather service, the National Institute of Meteorology (INMET), has issued two yellow alerts for Wednesday, Oct. 21. Yellow is the "Potential Danger" level. All times below are Brasília time.

The first alert covers heavy rain and runs from 12:01 a.m. to 11:59 p.m. It applies to 179 municipalities in the states of Acre, Amazonas, Mato Grosso, Pará, Rondônia and Roraima. Three state capitals fall inside it: Rio Branco, Manaus and Porto Velho.

The second alert covers storms. It starts at 3 p.m. (2 p.m. in Mato Grosso do Sul) and runs until 11:59 p.m., across 623 municipalities in Paraná, Santa Catarina, Rio Grande do Sul, Mato Grosso do Sul and São Paulo. No state capital is on that list. Residents of the interior of those states can check INMET's alert panel to see whether their own municipality is inside the area.

What the alerts say

For the heavy-rain area, INMET forecasts 20 to 30 millimeters of rain per hour, or up to 50 millimeters in a day, with winds of 40 to 60 km/h. The storm alert carries the same rain and wind figures, plus the possibility of hail. For both alerts, INMET rates the risk of power outages, falling tree branches and flooding as low. The heavy-rain alert also lists a low risk of lightning strikes, and the storm alert a low risk of crop damage.

When winds gust, the institute advises people not to shelter under trees and not to park vehicles near transmission towers or billboards. It also recommends avoiding electronic devices plugged into wall outlets. More information is available from Brazil's civil defense agency (Defesa Civil, phone 199) and the fire department (Corpo de Bombeiros, phone 193).

Forecast for the state capitals today

In the three capitals inside the heavy-rain alert, INMET's city forecast calls for showers. Porto Velho has a high of 34 °C and a low of 25 °C, with showers through the day, isolated thunderstorms in the afternoon and evening, and wind gusts. Rio Branco expects 34 °C and 23 °C, with showers in the afternoon and evening and isolated thunderstorms at night. Manaus sits at 35 °C and 25 °C, with showers in the morning and afternoon.

According to the model of the Norwegian meteorological service (MET Norway), Porto Velho has the largest estimated rainfall total over the next 24 hours among Brazil's 27 capitals, at 13.8 millimeters. Vitória, the capital of Espírito Santo, follows with 8.4 millimeters, then Rio Branco with 6.5 and Manaus with 6.3. These are model estimates.

Teresina is the hottest of the 27 capitals today, with an INMET forecast of a 39 °C high and a 25 °C low under few clouds. Cuiabá and Palmas come next, at 36 °C each. The South is cooler. Curitiba has 20 °C and 11 °C, Florianópolis 21 °C and 11 °C, and Porto Alegre at 23 °C and 13 °C. Curitiba could see isolated showers at night.

São Paulo is forecast at 24 °C and 13 °C, with mostly cloudy skies and isolated showers at night. Rio de Janeiro has 26 °C and 19 °C, also with isolated showers at night. Brasília is forecast at 32 °C and 19 °C, with few clouds in the morning and a chance of isolated rain from the afternoon. Belo Horizonte is looking at 30 °C and 18 °C, with a chance of isolated rain in the afternoon and evening.

Thursday (Oct. 22) and the days ahead

The storm alert widens on Thursday. INMET forecasts storms, again at the yellow level, for 2.853 municipalities in 15 federative units (states and the Federal District), from 12:01 a.m. to 11:59 p.m. Ten capitals are on the list: Rio Branco, Manaus, Porto Velho, Campo Grande, Belo Horizonte, Rio de Janeiro, São Paulo, Curitiba, Florianópolis and Porto Alegre.

The same day, from noon to 8 p.m., a yellow alert for low humidity covers 684 municipalities in 11 states, eight of them in the Northeast, including Teresina. Relative humidity should fall between 30% and 20%, with a low risk of wildfires and of health problems, according to INMET. The institute recommends drinking plenty of fluids and avoiding physical exertion and sun exposure during the driest, hottest hours.

On Friday (Oct. 23), the storm alert covers 2.812 municipalities in nine states across the South, Southeast and Center-West, with seven capitals: Campo Grande, Belo Horizonte, Rio de Janeiro, São Paulo, Curitiba, Florianópolis and Porto Alegre. A heavy-rain alert also applies to 43 municipalities in Acre, Amazonas and Rondônia, including Rio Branco and Porto Velho. On Saturday (Oct. 24), the storm alert continues for 2.168 municipalities in seven states, with Campo Grande, Rio de Janeiro, São Paulo, Curitiba, Florianópolis and Porto Alegre on the list.

In its city forecast for Thursday, INMET shows overcast skies in São Paulo (24 °C and 17 °C), with drizzle at night, and in Porto Alegre (26 °C and 15 °C), with drizzle through the day. Porto Velho is forecast at 32 °C and 24 °C, with isolated rain, and Teresina stays at a 39 °C high. Brasília is at 32 °C and 19 °C, with cloudy skies in the morning and afternoon.

The city forecast describes the weather in general terms. Where it differs from an alert, follow the alert, which is the official reference for the risk of heavy rain, wind and hail. The temperatures and rainfall totals cited are forecasts, not measurements. The alerts and forecasts were checked on the morning of Oct. 21 (Brasília time), and the alert areas may change during the day. The updated list is on the institute's official panel.

Sources

• INMET: weather alerts panel
• INMET: city weather forecast
• MET Norway: forecast data (CC BY 4.0 license)
• RaisLife: weather and forecast for the 27 capitals

Text by Rai, RaisLife's virtual reporter (artificial intelligence), with automated editorial review. Data: RaisLife weather panel.