It may sound like old news, but another cold front is already on its way to São Paulo, and we’ll tell you everything you need to know to prepare. The cold temperatures are expected to reach the state between this weekend and Monday, September 21.
However, the good news is that, before the front arrives, São Paulo is expected to experience a brief pre-frontal warming with hotter and more muggy conditions.
Shortly thereafter, the low-pressure system will increase atmospheric instability, bringing the cold front on Monday, complete with rain and thunderstorms—essential for anyone planning the São Pauloweather forecast for this period.
What is causing this new cold front in São Paulo?
The picture presented in the latest forecasts is more than just the usual arrival of cold air: it is the result of the convergence of several meteorological events.
First, the phenomenon is associated with a trough (an elongated band of low atmospheric pressure) located between Paraguay and southern Brazil. At the same time, the warm, humid air being carried toward the Southeast will intensify the heavy clouds, thunderstorms, and lightning in the city’s skies.
Temperatures are likely to drop as a result of this collision zone between the warm air and the cold air mass advancing across the continent.
As a result, the atmosphere becomes unstable, and shortly thereafter, cold air will prevail and cause temperatures to drop. This intensifies the instability and strengthens the rain showers.
However, what has been causing this high frequency of cold fronts is the intense activity of a subtropical jet stream further north, which has helped trap weather systems over the Southeast region. The negative phase of the Antarctic Oscillation also facilitates the arrival of cold air masses in South America.
And, of course, the El Niño phenomenon also influences the climate as a backdrop, leading to an increasingly frequent pattern of above-average rainfall in southern Brazil and in some regions of São Paulo.
Expected temperatures for the weekend forecast:
- Saturday, September 19: Low 16°C | High 24°C to 26°C
- Sunday, September 20: Low 18°C | High 25°C
- Monday, September 21: Low 20°C | High 29°C to 30°C
The overall cooling will not be uniform across the entire state. According to forecasts, regions at higher elevations and with more cloud cover, or those more influenced by maritime conditions, tend to feel the cold more intensely.
The good news is that there’s a brief spell of warm weather this Monday, with some parts of the capital approaching or reaching 30°C. However, this is temporary, and soon after, the cold front will return with full force.
