Porto Alegre, the capital of Rio Grande do Sul state, sits in the far south of Brazil at the head of the Lagoa dos Patos lagoon, on low-lying ground near sea level at approximately 30.03°S, 51.23°W. Its southerly latitude gives it a humid subtropical climate (Köppen Cfa) — hot summers and cool winters — with four genuine seasons, rain spread through the year, and a wider temperature range than tropical Brazil. Being in the Southern Hemisphere, its seasons are reversed relative to the Northern.

Summer, from December to February, is hot and humid, with January the warmest month — average highs around 30–31°C — and hot spells that can exceed 35–40°C, made to feel heavier by the humidity off the lagoon. Afternoon thunderstorms are common, sometimes severe, and the low-lying, near-sea-level setting keeps the warm season sultry.

Winter, from June to August, is cool and damp, with July the coolest month — average highs around 19°C and lows near 9–10°C, occasionally dropping to frost on clear nights during cold outbreaks from the south. Grey, wet, chilly spells are common as Antarctic-origin cold fronts sweep through, and genuine cold, though brief, is a real feature — unlike most of Brazil.

Porto Alegre is fairly wet, receiving on the order of 1,300–1,500 mm of rain a year, spread fairly evenly through every month with no dry season, though it can arrive in heavy bursts; the region has suffered catastrophic flooding, as in the devastating floods of 2024. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Porto Alegre's far-southern position gives it four distinct seasons and a genuine cool winter, unlike tropical Brazil, with weather driven by the clash of warm tropical air and cold fronts sweeping up from the Antarctic. Its low-lying setting at the head of a vast lagoon system leaves it exposed to serious flooding when heavy, persistent rain raises the rivers, as the record-breaking 2024 disaster showed.

To follow any single measurement in Porto Alegre more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.