Summer 2024-2025 was the sixth hottest in Brazil since 1961

The 2024/2025 summer, which ended this Thursday (20), was the sixth hottest in Brazil since 1961 (Table 1), with a temperature 0,34°C above the historical average for the period from 1991 to 2020.

Temperatures were above average across much of Brazil (Figure 1). The highest maximum temperatures were observed, mainly in Rio Grande do Sul, due to the occurrence of three heat waves that affected the state: between January 17 and 23, 2025, February 2 and 12, 2025, and March 1 and 8.

Even under the influence of La Niña, which tends to reduce the average global temperature, this summer was among the ten hottest in the series. The data presented in Table 1 show that temperatures in Brazil during the summer have been above average since the 1990s.

The years 2023/2024, 2015/2016, 1997/1998 and 2009/2010 were under the influence of the El Niño phenomenon, which is the above-average warming of the waters of the Equatorial Pacific Ocean, increasing the temperature increase in several regions of the planet.

The fact is that, for Brazil, this last decade was hotter than the previous one, as warned by the World Meteorological Organization (WMO), which emphasizes the increase in greenhouse gas emissions into the atmosphere and global warming.

Summer with lots of rain

In parallel with the high temperatures, the summer of 2024-2025 was also marked by heavy rainfall in the country, mainly in much of the North Region, Maranhão and northern Piauí, with volumes exceeding 700 mm (blue tones - Figure 2), and many locations exceeding the historical average.

The constant storms that hit the northern part of the country during the summer were mainly responsible for the Intertropical Convergence Zone (ITCZ) meteorological system, which is formed by the confluence of trade winds from the northeast, originating in the Northern Hemisphere, and also winds from the southeast, originating in the Southern Hemisphere.

Rainfall exceeded 500 mm in the Center-North of the country (blue tones - Figure 2), except in Roraima, in the center-east of the Northeast Region, in the center-south of Mato Grosso do Sul, in the west of São Paulo, in the north of Minas Gerais, in Espírito Santo, in Rio de Janeiro, as well as in the central and western part of the South Region, where lower volumes were observed (green and orange tones - Figure 2).

In the Central-West and Southeast regions, rainfall was predominantly below average, with values ​​exceeding 600 mm in the north-central region of Mato Grosso and in specific areas of Goiás and São Paulo (blue tones - Figure 2). In the other areas, rainfall accumulations were lower, ranging from 300 to 500 mm. This summer, there were three episodes of the South Atlantic Convergence Zone (ZCAS): the first between December 27 and 31, 2024, the second between January 6 and 15, 2025, and the last between January 31 and February 5, 2025.

In the Southern Region, the passage of frontal systems and areas of instability resulted in rainfall above 500 mm over the eastern part of Paraná and Santa Catarina (blue tones - Figure 2). In the other areas of the region, rainfall was below average, mainly in the west of Rio Grande do Sul, where rainfall volumes during the summer were below 250 mm (orange tones - Figure 2), while the historical average for this region during this period varies between 400 and 500 mm.