According to the Köppen classification, the city has a humid subtropical climate (Cfa). In summer (January through March), the mean low temperature is about 19 °C (66 °F) and the mean high temperatures is near 28 °C (82 °F). In winter, temperatures tend to range between 12 and 22 °C (54 and 72 °F).
The record high temperature was 37.8 °C (100.0 °F) on October 17, 2014 and the lowest −3.2 °C (26.2 °F) on June 25, 1918. The Tropic of Capricorn, at about 23°27′ S, passes through north of São Paulo and roughly marks the boundary between the tropical and temperate areas of South America. Because of its elevation, however, São Paulo experiences a more temperate climate.
The city experiences four seasons. The summer is warm and rainy. Autumn and spring are transitional seasons. Winter is the most cold season, with cloudiness around town and frequently polar air masses. Frosts occur sporadically in regions further away from the center, in some winters throughout the city. Regions further away from the center and in cities in the metropolitan area, can reach temperatures next to 0 °C (32 °F), or even lower in the winter.
Rainfall is abundant, annually averaging 1,454 millimeters (57.2 in). It is especially common in the warmer months averaging 219 millimeters (8.6 in) and decreases in winter, averaging 47 millimeters (1.9 in). Neither São Paulo nor the nearby coast has ever been hit by a tropical cyclone and tornadic activity is uncommon. During late winter, especially August, the city experiences the phenomenon known as “veranico” or “verãozinho” (“little summer”), which consists of hot and dry weather, sometimes reaching temperatures well above 28 °C (82 °F). On the other hand, relatively cool days during summer are fairly common when persistent winds blow from the ocean. On such occasions daily high temperatures may not surpass 20 °C (68 °F), accompanied by lows often below 15 °C (59 °F), however, summer can be extremely hot when a heat wave hits the city followed by temperatures around 34 °C (93 °F), but in places with greater skyscraper density and less tree cover, the temperature can feel like 39 °C (102 °F), as on Paulista Avenue for example. In the summer of 2014, São Paulo was affected by a heat wave that lasted for almost 4 weeks with highs above 30 °C (86 °F), peeking on 36 °C (97 °F). Secondary to deforestation, groundwater pollution, and climate change, São Paulo is increasingly susceptible to drought and water shortages.
Due to the altitude of the city, there are only few hot nights in São Paulo even in the summer months, with minimum temperatures rarely exceeding 21 °C (70 °F). In winter, however, the strong inflow of cold fronts accompanied by excessive cloudiness and polar air cause fairly low temperatures, even in the afternoon.
Afternoons with maximum temperatures ranging between 13 and 15 °C (55 and 59 °F) are common even during the fall and early spring. During the winter, there have been several recent records of cold afternoons, as on July 24, 2013 in which the maximum temperature was 8 °C (46 °F) and the wind chill hit 0 °C (32 °F) during the afternoon.
São Paulo is known for its rapidly changing weather. Locals say that all four seasons can be experienced in one day, similar to Melbourne, Australia. In the morning, when winds blow from the ocean, the weather can be cool or sometimes even cold. When the sun hits its peak, the weather can be extremely dry and hot. When the sun sets, the cold wind comes back bringing cool temperatures. This phenomenon happens usually in the winter.