Climatic map of the Province of Buenos Aires, Argentina
The climate of the province of Buenos Aires is extremely benign for human activities: it is temperate, with four marked seasons and reliable rainfall on most regions. The province can be divided in four main climatic regions: the southwestern, drier region; the cool Atlantic region; the northern and eastern humid region, and the Delta region, with the warmest, wettest climate.
The northern region has warm, humid summers, with days between 28 and 32 °C and nights between 16 and 20 °C, pleasant falls, cool, drier winters with highs between 13 and 18 °C and nights between 2 and 5 °C, and windy, variable springs. Heat waves may bring days with temperatures over 38 °C, but these do not usually last very long, as cold fronts bring thunderstorms and cooler days, with night temperatures often falling down to 12 °C. Winter cold waves may bring days with highs about 8 °C, and lows below -4 °C, with extremes down to -8 °C. Snow is uncommon, but there have been accumulations on several occasions in the past. Precipitation ranges from 750 to 1,100 mm per year.
The Delta region is slightly warmer, especially at night, due to the presence of water and the northerly location. Summer nights tend to be stickier, and winters can be damp and foggy, with most nights between 4 and 8 °C. Frost is still to be expected, but temperatures will almost never fall below -4 °C, and snow has fallen only twice in the last century. Precipitation ranges from 1,000 to 1,300 mm and falls throughout the year. The city of Buenos Aires is surrounded by a climate similar to the northern part of the province, but the city itself resembles more the Delta climate, with less frost.
The southwestern region is the driest region, and it experiences a more marked differences in temperatures. Summers are often hot, between 30 and 35 °C, but nights are usually comfortable (14 to 18 °C. Thunderstorms are less frequent, but can be very violent in nature. Frost can make an appearance as early as March, but usually first comes in April. Winters are cool and dry, with days between 10 and 16 °C and nights between -1 and 4 °C. Frost occurs on an almost daily basis, with temperatures below -6 °C not uncommon, and down to -12 °C recorded in some areas. Snowfall may occur every once in a while, but accumulations are usually small. Total precipitation ranges from 500 to 750 mm, with slightly rainier springs and falls.
The Atlantic region sees very moderate weather: the ocean is cold (17 to 20 °C in the summer) and sea breezes often bring chilly weather until midsummer. The hottest months average 25 to 27 °C with nights between 12 and 16 °C, providing a perfect relief for the inhabitants of the hotter interior. Fall is often rainy, and winters can be windy and chilly: temperatures average from 10 to 15 °C, and nights from 1 to 5 °C. There can be long periods of drizzly weather and constant temperatures of about 7 °C. Frost is common but temperatures will rarely fall below -5 °C, and snow falls sometimes, but accumulations are only to be expected every few years. Precipitation ranges from 700 to 950 mm. The Sierras de la Ventana (up to 1,200 metres) experience cooler weather, especially at night.
The geography of the province is crossed by occasional west Pampero winds. The southern Sudestada produces storms and temperature drops, most notably the Santa Rosa storm, which takes place every year almost exactly on August 30.