Porto Alegre Weather by Month

Porto Alegre has a humid subtropical climate (Köppen Cfa) with four distinct seasons. Summers are hot and humid, winters are mild to cool, and rainfall is spread evenly throughout the year at around 1,300mm (51 inches) annually. The city sits at only 10 metres above sea level on the Guaíba River, which moderates temperatures slightly but also contributes to high humidity levels year-round.

Porto Alegre Weather by Month: Summer (December to February)

Summer in Porto Alegre runs from December through February. January is the hottest month with average highs of 30°C (86°F) and lows around 21°C (70°F). Heat waves can push temperatures above 38°C (100°F) for several days at a time, particularly in January. Afternoon thunderstorms are common — the city averages 10 to 12 rainy days per month during summer, with January rainfall averaging 110mm (4.3 inches). Humidity hovers around 75%, making the heat feel heavier than the numbers suggest. UV levels are extreme (11+) in December and January, so sunscreen is essential even on cloudy days. On the plus side, summer brings 13.5 to 14 hours of daylight and the city’s parks and outdoor bars fill up after sunset when temperatures drop to a more comfortable 24°C to 26°C (75°F to 79°F).

Porto Alegre Weather by Month: Autumn (March to May)

Autumn is the most comfortable season in Porto Alegre. March starts with summer-like warmth (average high 29°C / 84°F) but by May daytime highs drop to 22°C (72°F) and nights cool to 13°C (55°F). Rainfall remains steady at 100 to 120mm per month, but the frequency of thunderstorms decreases. April and May are particularly pleasant — sunny days with temperatures in the low-to-mid 20s Celsius (70s Fahrenheit) and lower humidity around 65%. This is when the city’s jacaranda trees bloom purple along avenues like Avenida Carlos Gomes. Daylight hours shrink from 12.3 in March to 10.6 in May.

Porto Alegre Weather by Month: Winter (June to August)

Winter is mild by Brazilian standards but chilly for visitors from tropical regions. July is the coldest month with average highs of 19°C (66°F) and lows around 10°C (50°F). Cold fronts from the South Atlantic can push overnight lows to 2°C to 5°C (36°F to 41°F), and frost occurs occasionally in the outskirts. Snow is virtually unheard of — the last recorded snowfall was in 1879. June is the wettest month of the year with 140mm (5.5 inches) of rain, while July and August average 120mm. Winter days are short (10.2 to 10.8 hours of daylight) and overcast skies are common. Wind chill from the pampero wind (a cold southwesterly from Argentina) can make 15°C (59°F) feel like 8°C (46°F), so pack a warm jacket even if the forecast looks mild.

Porto Alegre Weather by Month: Spring (September to November)

Spring is a transitional season with rapidly warming temperatures. September starts cool (average high 22°C / 72°F, low 12°C / 54°F), but by November highs reach 28°C (82°F) and lows 17°C (63°F). October is one of the rainiest months at 130mm (5.1 inches), often with intense but short-lived downpours. Humidity climbs back to summer levels (70% to 75%) by November. The season is windy, with average speeds of 15 to 20 km/h (9 to 12 mph), which helps offset the rising humidity. Spring is also when the city’s many parks turn lush green — Parque Farroupilha and Parque Marinha do Brasil are at their most photogenic in October and November.

Porto Alegre Weather by Month: Climate Data