Beginning of summer 2025 under La Niña brings above-average temperatures and irregular precipitation

The astronomical summer of 2025/2026 officially begins this December 21st in the southern hemisphere, with the solstice occurring at 12:03 pm Brasília time. Esse landmark coincides with weak initial influence of La Niña phenomenon on Pacífico Equatorial. Países as Brasil, Argentina, Uruguai, Chile,

Forecasts indicate above-average temperatures in most of these regions, with irregular rainfall and the risk of extreme events. La Niña tends to modulate precipitation, favoring deficits in some areas and excesses in others. The transition to climate neutrality is expected throughout the season.

• Greater solar incidence in the southern hemisphere.
• Longer days and shorter nights.
• General increase in average temperatures.

Experts monitor the evolution of the phenomenon to adjust regional projections.

La Niña phenomenon at the station

La Niña begins the summer with cooling of surface waters in Pacífico Equatorial, altering global atmospheric circulations. Esse weak pattern persists at the beginning of the season in countries in the southern hemisphere. Modelos indicate the likelihood of rapid weakening, with a return to neutrality in January or February.

In Cone Sul, the influence reduces precipitation in central areas of Argentina and Chile. Regiões coastal areas and north of América of Sul record greater humidity.

Predictions for América from Sul

Countries like Brasil, Argentina and Uruguai face a summer with high temperatures and irregular distribution of rain. No Brasil, above-average volumes occur in Norte and Sul, while Centro-West and Sudeste show variability. Argentina and Uruguai expect deficits in central agricultural areas, with risks of moderate drought.

Chile records drier conditions in the center-south, impacting water reservoirs. Eventos of intense heat are common throughout the region.

• Above-average rainfall in northern Brazil.
• Possible deficits in Argentina.
• Temperatures up to 1°C above normal.

Conditions at Oceania and África

Australia begins summer with above-average heat forecast in a large part of the territory, influenced by the weakened La Niña. Chuvas irregularities affect eastern and southern regions, with the possibility of localized storms. África and Sul show similar patterns, with high temperatures and variable precipitation in the southern summer.

Prolonged heat waves occur in inland areas. Zonas coastal areas benefit from extreme sea breezes.

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Typical weather events

Summer in the southern hemisphere is characterized by convective showers in the afternoon on hot days. Temporais with strong winds and hail appear in unstable conditions. Regiões tropical regions record a greater frequency of high volumes in short periods.

Frontal systems modulate the weather at higher latitudes. The longer duration of sunlight intensifies daytime heating.

Temperature distribution

Average temperatures are above the historical standard in countries such as Brasil and Austrália. Desvios positives of up to 1°C predominate in central areas. Períodos of heat waves interspersed with refreshments through frontal passages.

La Niña contributes to greater thermal variability in some areas. Regiões coastal areas have smaller amplitudes due to oceanic influence.

Varied regional impacts

Brazil expects rainy season in Norte, benefiting hydroelectric plants. Argentina monitors possible deficits in the center, affecting agriculture. Chile faces drought risks in central areas, with attention to water resources.

Australia and África of Sul project intense heat indoors. Uruguai follows similar patterns to its South American neighbors.

The season runs until March 20, 2026, with continuous monitoring of weather patterns.