Climate Shift Index Alert•February 20, 2025
Climate change fuels record February heat in Brazil ahead of Carnival
Update: March 3, 2025 In February 2025, our forecast alert linked an extreme heat event in South America to climate change. A persistent area of high pressure drove temperatures above 38°C (100°F), prompting the impacts listed in the alert below. NASA confirmed the intensity of this heatwave — unusual even during Brazil’s summer — by combining satellite observations with predicted temperatures. Brazil’s National Institute of Meteorology (INMET) reported multiple locations across the state of Rio de Janeiro exceeding 40°C (104°F) on February 17, including Silva Jardim, which hit 42°C (108°F). The extreme heat persisted throughout the week before shifting south into Argentina. |
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More than 127 million people across Brazil are experiencing heat made at least five times more likely because of climate change from February 14-20. The heat has prompted authorities to issue excessive heat alerts as the nation prepares for Carnival, a week-long festival and the most popular holiday in Brazil.
Cities are ramping up hydration stations and public health services to address rising cases of dehydration, heat exhaustion, and heat stroke cases. Meanwhile, water shortages and limited access to air conditioning are disrupting daily life.
How has climate change influenced this heat?
Temperatures as high as 30°C to 44°C (86°F to 111°F) are well above the mid-to-late February normal, with some locations in Brazil experiencing temperatures 3°C to 8°C (5.4°F to 14.4°F) above what is normal for this time of the year.
These above-average temperatures are forecast to persist through at least the end of February, and likely longer.
Daily maximum temperatures reached a Climate Shift Index (CSI) level of 5 in cities across multiple regions of Brazil, including northeast, southeast, and south Brazil from February 14-18.
CSI levels of 5 are forecast to impact most states in northeast, central-west, southeast, and south Brazil on February 19 and 20.
CSI level 5 indicates that human-caused climate change made this extreme heat at least 5 times more likely, signifying an exceptional climate change event.
Preliminary data indicates that more than 127 million people in Brazil will have experienced at least one day with CSI level 5 from February 14 to February 20.
More than 170 million people in Brazil will have experienced at least one day with CSI level 3 — indicating a very strong climate change influence — from February 14 to February 20.
Impacts:
Rio de Janeiro experienced its highest temperature in at least the past decade on Monday, February 17th, reaching a high of 44°C (111°F).
In January, over 3,000 people sought treatment at municipal emergency services due to extreme heat, according to Rio de Janeiro’s health secretary—more than twice the number recorded in recent years.
This intense heatwave has delayed the start of the school year in Rio Grande do Sul, due to classrooms lacking adequate ventilation and student water supplies.
A lack of rain has made this one of the driest Februarys on record, leading to water shortages for residents in favelas and neighborhoods of Rio de Janeiro, increasing the concern for heat illness and dehydration.
City | Date of Highest Temperature | Highest Temperature (°C) | Days Above CSI 3 (Tavg) | Days Above CSI 5 (Tavg) | Number of Days with Temperature Max Above 30°C |
|---|---|---|---|---|---|
Foz do Iguaçu | February 18, 2025 | 38.8 | 5 | 2 | 7 |
São Gonçalo | February 18, 2025 | 37.5 | 2 | 0 | 7 |
Petrolina | February 20, 2025 | 37.0 | 4 | 3 | 7 |
Praia Grande | February 17, 2025 | 36.7 | 1 | 1 | 5 |
São Vicente | February 17, 2025 | 36.7 | 1 | 1 | 5 |
Campos dos Goytacazes | February 18, 2025 | 36.5 | 5 | 2 | 7 |
Governador Valadares | February 18, 2025 | 36.4 | 5 | 1 | 7 |
Volta Redonda | February 18, 2025 | 36.1 | 5 | 5 | 7 |
Bauru | February 20, 2025 | 35.4 | 6 | 5 | 7 |
Joinville | February 17, 2025 | 34.8 | 2 | 1 | 3 |
Cuiabá | February 20, 2025 | 34.7 | 4 | 2 | 5 |
Várzea Grande | February 20, 2025 | 34.7 | 3 | 2 | 5 |
Cariacica | February 17, 2025 | 34.5 | 6 | 5 | 7 |
Petrópolis | February 18, 2025 | 34.4 | 4 | 1 | 6 |
Piracicaba | February 17, 2025 | 34.4 | 6 | 5 | 7 |
Ribeirão Preto | February 17, 2025 | 34.3 | 6 | 5 | 7 |
What do experts say?
Dr. Kristina Dahl, VP for Science at Climate Central, said:
“This exceptional heat in Brazil would be essentially impossible without the influence of climate change,” said Dr. Kristina Dahl. ”As global temperatures continue to rise due to fossil fuel emissions, we can expect more heat waves to coincide with major cultural events like Carnival and sports events like the Rio Open.”
To request an interview with a Climate Central scientist, please contact Abbie Veitch at aveitch@climatecentral.org.
How do we know climate change is influencing this heat?
The Climate Shift Index uses peer-reviewed methodology and real-time data to estimate how climate change has increased the likelihood of a particular daily temperature.
We compare the likelihood that these temperatures would occur in a world without carbon emissions released by humans, versus in today’s world with decades of carbon emissions building up in the atmosphere. This is an established scientific method to determine how much climate change has or has not affected individual extreme weather events.