São Paulo Heatwave: Record Christmas Temperatures Expected

São Paulo is experiencing an intense heatwave with temperatures reaching 40°C on Avenida Santo Amaro. The National Institute of Meteorology (Inmet) has issued alerts for extreme heat throughout the week. On Christmas Day, the capital could reach 36°C, potentially setting a new December temperature record.

The previous record for the year was 35.1°C on October 6. The heat is caused by a hot and humid air mass affecting the Southeast region, creating sunny days with well-above-average afternoon temperatures. Humidity levels have dropped to around 35%, contributing to the intense heat. The weather pattern includes warm, muggy mornings and isolated afternoon rain showers.

The forecast for Christmas Day shows a low of 23°C and high of 36°C with thunderstorms expected in the afternoon and evening. Friday will see similar conditions with temperatures reaching 32°C. Saturday is expected to be more unstable with stronger afternoon rain. The combination of strong heating and sea breeze infiltration creates conditions for rapid isolated rainfall between mid-afternoon and early evening across the capital and surrounding metropolitan areas.

São Paulo faces the possibility of a historic temperature record on Christmas Day. The city could reach 36°C, which would mark the highest temperature ever recorded in December. This potential record comes as the first week of summer brings intense heat across parts of the country.

The current heatwave has already produced extreme temperatures. A thermometer on Avenida Santo Amaro in South São Paulo registered 40°C earlier this week. Inmet has maintained heat alerts throughout the region due to these dangerous conditions.

The previous temperature record for 2025 was set on October 6, when the city reached 35.1°C. If Christmas Day temperatures hit the predicted 36°C, it would surpass that mark significantly. The heat is being driven by a persistent hot and humid air mass over the Southeast region.

A hot and humid air mass continues to dominate the Southeast region of Brazil. This weather system guarantees sunny days with temperatures well above the historical average for the afternoon period. The CGE of the São Paulo City Hall confirms these conditions will persist throughout the week.

Humidity levels have declined significantly during this heatwave. The lowest humidity values are approaching 35%, which contributes to the intensity of the heat sensation. Despite the low daytime humidity, mornings remain muggy and uncomfortable.

The mornings feature a muggy atmosphere that will continue until the weekend. These warm, humid conditions create discomfort, especially during the early hours. The combination of high temperatures and variable humidity creates challenging conditions for residents.

Christmas Day, Thursday the 25th, will see unaltered weather conditions. The day begins with a muggy dawn and few clouds in the sky. Strong sunshine will be present from sunrise throughout the morning hours.

As afternoon approaches, conditions change rapidly. Strong heating combined with maritime breeze infiltration creates favorable conditions for rain. There is a significant probability of isolated rapid rainfall between mid-afternoon and early evening across the capital and neighboring cities in Greater São Paulo.

The detailed forecast from Climatempo shows specific conditions for each day:

• Thursday (25th): Minimum 23°C, Maximum 36°C. Morning sun with afternoon thunderstorms and storms. Humidity between 39% and 86%.
• Friday (26th): Minimum 23°C, Maximum 32°C. Morning sun with increasing clouds, afternoon and evening rain showers. Humidity between 46% and 86%.
<.As Thursday (25th): Minimum 23°C, Maximum 36°C. Morning sun with afternoon thunderstorms and storms. Humidity between 39% and 86%.

Friday (26th): Minimum 23°C, Maximum 32°C. Morning sun with increasing clouds, afternoon and evening rain showers. Humidity between 46% and 86%.

Saturday (27th): Minimum 21°C, Maximum 33°C. Morning sun between clouds, strong afternoon rain with evening storms. Humidity between 47% and 97%.

Friday maintains the established weather pattern. Residents can expect morning sunshine followed by cloud buildup throughout the day. Rain showers will continue between afternoon and night, similar to Christmas Day conditions.

Saturday shows signs of increasing weather instability. The morning will feature sun between many clouds, creating a more dynamic sky. The forecast predicts stronger rain during the afternoon hours, with additional showers continuing into the night.

This progression suggests the heatwave may be accompanied by more intense precipitation as the weekend approaches. The combination of extreme heat and developing storms creates a complex weather situation for the São Paulo metropolitan area.