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The first cold front of autumn hits the state of São Paulo starting this Tuesday with a forecast of strong rain showers, storms, lightning, hail, and wind gusts, but the Civil Defense and Climatempo warn that the cold does not accompany the system because April will be marked by atmospheric blockages that keep the heat above average with the possibility of a heat wave
The first cold front of autumn arrives in the state of São Paulo starting this Tuesday (31), according to the Civil Defense.
With the gradual advance of the system, rain showers, storms, and unstable weather are forecasted in several regions of São Paulo.
The first cold front of autumn brings a risk of storms with lightning, hail, and wind gusts especially in the eastern part of the state, but the cold itself does not come now: temperatures remain high and the stuffiness persists even during the passage of the system.
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What surprises in this first cold front of autumn is that it does not come accompanied by a drop in temperature.
April will be dominated by above-average heat in São Paulo, the South region, and Mato Grosso do Sul, with the possibility of a heat wave forming, according to Climatempo.
Significant cold is only expected to appear in the last week of April, when a more intense cold front may finally lower the thermometers.
What the first cold front of autumn will cause in São Paulo this week
The first cold front of autumn begins to affect the state of São Paulo this Tuesday, with isolated moderate to strong rain, lightning, and winds, mainly in eastern São Paulo.
Even with high temperatures and a feeling of stuffiness, the approach of the system already brings atmospheric instability.
The change in weather becomes more noticeable on Wednesday (April 1), when the combination of the first cold front of autumn, accumulated heat, and humidity is expected to cause more widespread rain showers.
The risk includes storms with wind gusts, lightning, and hail, with the possibility of localized impacts in different regions of the state.
The Civil Defense of São Paulo issued a warning for the population to be alert to flooding, falling trees, and landslides in vulnerable areas during the passage of the first cold front of autumn.
Despite the instability, the rain is expected to be concentrated in strong and quick showers, not in prolonged periods of precipitation, which is typical of cold fronts passing through still very warm environments.
Why the first cold front of autumn does not bring cold to São Paulo
The explanation for the first cold front of autumn arriving without cold lies in the atmospheric blockages that dominate Brazil’s climate at the beginning of April.
High-pressure systems over the country are preventing the entry of cold air inland, diverting cold fronts to the ocean and keeping warm air stationary over São Paulo and much of the Southeast.
These blockages are common during transitional periods between seasons and create a climate pattern where humidity decreases, rainfall diminishes, and heat intensifies throughout most of the month.
The cold fronts that manage to form pass along the coast of the South and Southeast, but the cold air remains concentrated over the ocean and does not penetrate inland.
The result is that the first cold front of autumn causes instability and storms, but the cold air mass that should follow it is blocked before it arrives, and São Paulo remains warm.
In practice, this means that residents of São Paulo will face heavy rain in the middle of a hot day, something that seems contradictory but is exactly what happens when a cold front passes without the strength to lower temperatures.
April with above-average heat and risk of heat wave in São Paulo
Climatempo’s forecasts indicate that April will have above-average temperatures in São Paulo, the South region, and Mato Grosso do Sul.
The heat will not only be above normal: there is a possibility of a heat wave forming during the month, which would mean several consecutive days with temperatures well above the average for the period.
For those who expected autumn to bring mild temperatures and cooler nights, the scenario in April is the opposite of what was expected.
The atmospheric blockages reduce air humidity, hinder the formation of rain clouds, and create conditions for heat to accumulate day after day.
The combination of intense heat with dry air can cause respiratory discomfort, increased energy consumption with air conditioning, and health risks for the elderly and children, especially if the heat wave is confirmed.
Despite the prevailing heat, rain in April in the state of São Paulo is expected to remain within historical averages, but concentrated in isolated episodes of instability like the one accompanying the first cold front of autumn.
When does the real cold arrive in São Paulo after the first cold front of autumn
The most significant temperature change is expected for the last week of April.
A more intense cold front is expected to advance through the country at the end of the month, causing a sharp drop in temperatures in the South and in areas of the Southeast and Midwest.
This cold front at the end of April is different from the first cold front of autumn arriving this week: it should have enough strength to break the atmospheric blockages and push cold air inland.
Until then, São Paulo is expected to alternate between hot, dry days with occasional rain and instability when smaller systems manage to approach.
For those expecting the typical autumn cold in São Paulo, the message is clear: the first cold front of autumn brings rain and storms, but the cold itself only appears at the end of April, and until then, the heat dominates.
Monitoring the forecasts in the coming days will be important to confirm whether the heat wave materializes and how long the atmospheric blockage will last before the cold can finally enter.
Strong rain, hail possible, and an autumn that seems like summer
The first cold front of autumn arrives in São Paulo this Tuesday with a risk of storms, hail, and wind gusts, but without bringing the cold that everyone expects.
April will be dominated by above-average heat, atmospheric blockages that divert cold air to the ocean, and the possibility of a heat wave that may last for days.
The real cold is only expected to appear in the last week of the month, with a more intense cold front. Until then, the first cold front of autumn is just the beginning of a month that will test the patience of those who already wanted to take their coats out of the closet.
Have you already felt the effects of the first cold front of autumn in your city? Were you expecting cold and got heat instead? Do you think this heat wave in the middle of autumn is normal or is it becoming more frequent? Leave your comments and share this article with those who need to prepare for the weather this week.
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