Intense Heatwave Grips Central-South Brazil as Winter Nears End, Temperatures Soar Above 40°C

An intense mass of hot air has settled over Central-South Brazil, driving temperatures significantly above seasonal averages and marking an atypical conclusion to winter. Forecasts indicate that highs could exceed 40°C in various areas, with some locations already recording temperatures as high as 42.9°C. This event represents the sixth heatwave to affect Brazil in 2025, impacting millions across multiple states.

Widespread High Temperatures and Affected Regions

Since the beginning of September, a significant warming trend has been observed across a broad swathe of Brazil. States such as Mato Grosso do Sul, Mato Grosso, Goiás, and Tocantins have already experienced temperatures surpassing 41°C during the first half of the month. On September 12, the municipality of São Miguel do Araguaia in Goiás registered 42.9°C, making it the highest temperature recorded in Brazil so far this year. Rondonópolis, in southeastern Mato Grosso, also reported 42°C on a recent Saturday.

The National Institute of Meteorology (INMET) and other meteorological services predict that this intense heat will persist until at least September 22, coinciding with the official start of spring. Temperatures are expected to remain 5°C or more above average in several interior states, including Maranhão, Tocantins, Goiás, Minas Gerais, São Paulo, Mato Grosso do Sul, and parts of Mato Grosso. Cities like Cuiabá and Palmas are forecast to experience daily highs above 35°C, accompanied by unseasonably warm nights.

Atypical Winter Conditions and Climate Change Context

The current heatwave is considered highly unusual for the end of winter in the Southern Hemisphere. Experts attribute the increasing frequency and intensity of such events to climate change. A study by World Weather Attribution indicated that unseasonal heat in South America was at least 100 times more likely due to human-caused climate change, contributing to temperatures that are 1.4-4.3°C hotter. While natural phenomena like El Niño can play a role, climate change is identified as the primary driver.

Past years have also seen similar anomalies; for instance, São Paulo and Cuiabá recorded their warmest winters since 1961 in 2023. This trend has led some experts to suggest that 'winter is disappearing' in parts of South America, with heatwaves becoming a more common and severe occurrence.

Impacts and Public Health Warnings

The prolonged period of high temperatures and dry conditions poses significant risks across the affected regions.

• Wildfire Risk: The dry air, with humidity levels dropping below 12% in areas like Goiás, Mato Grosso, Tocantins, and the interior of São Paulo, significantly elevates the risk of wildfires. Smoke from such fires can severely impact air quality, leading to respiratory issues.
• Public Health: Authorities have issued excessive heat alerts, urging residents to take precautions. Measures include setting up hydration stations and increasing public health services to address potential cases of dehydration, heat exhaustion, and heat stroke.
• Agriculture: The lack of significant rainfall, which is not expected to intensify until late September, is a concern for agricultural planning, particularly for soybean producers. Previous heatwaves have also impacted crops like sugarcane and corn.
• Infrastructure: Increased demand for electricity due to air conditioning use could strain power grids.

The situation underscores the growing challenges faced by Brazil in adapting to more extreme and frequent weather events.