Last updated: August 21, 2025
In September, Porto Alegre experiences a dynamic transition into spring, characterized by fluctuating temperatures that range from a chilly minimum of 7°C (45°F) to a sweltering maximum of 36°C (96°F). The average temperature hovers around a comfortable 18°C (65°F), making it an appealing time for outdoor activities. However, this month also brings its fair share of precipitation, with about 155 mm (6.1 in) of rain spread over 12 days, contributing to a notably high humidity level of 84%. Visitors and locals alike can expect a mix of warm sunshine and occasional showers, ideal for embracing the vibrant atmosphere of early spring in this Brazilian city.
In September, Porto Alegre begins to shake off the lingering chill of winter, with temperatures gradually rising. The month starts with a minimum of 7°C (45°F), offering a crisp but inviting atmosphere. As the days progress, the average temperature climbs to a comfortable 18°C (65°F), perfect for enjoying the city's vibrant outdoor scenes. With a maximum reaching up to 36°C (96°F), the warmth signals the onset of spring in Brazil, making September an ideal time to explore the blossoming parks and lively streets. This transitional month not only showcases a steady increase in temperatures but also sets the stage for the warmer months ahead.
September marks a significant shift in the precipitation patterns of Porto Alegre, Brazil, with average rainfall reaching 155 mm (6.1 in), making it one of the wettest months of the year. This uptick is accompanied by an increase in rainy days, totaling 12, which aligns with the transition into the spring season. Notably, September's precipitation surpasses both the previous months and those that follow, such as October with 139 mm (5.5 in) and November at 112 mm (4.4 in). This trend highlights September as a peak month for rainfall, often serving as a preparatory period for the more abundant rains of spring. The tropical climate of the region ensures that Porto Alegre experiences a vibrant and lush transition, making it a captivating time for nature and local festivities.
In September, Porto Alegre experiences a shift towards milder humidity levels, averaging at 84%. This marks a subtle decline from the peak humidity reached earlier in the year, with the late summer months of January through March hovering around 77% to 79%. As the city transitions into spring, humidity gradually increases, reaching 82% in July and peaking at 87% in May. Despite a slight decrease in September, the overall trend showcases a generally humid environment, reinforcing Porto Alegre's reputation for lush greenery and vibrant landscapes as it edges closer to the warmer months ahead.
In September, Porto Alegre experiences a UV Index of 9, placing it in the very high exposure category, with a burn time of just 15 minutes. This marks a slight decrease from the intense summer months, where values peak at 14 in January and December. Despite the seasonal transition, residents and visitors should remain vigilant, as September continues to pose significant sun exposure risks. As the year progresses, the UV Index trends highlight a notable fluctuation, with the final quarter of the year bringing both heightened sun safety awareness and the anticipation of the strong UV rays that return in the upcoming months. For more detailed information, visit Porto Alegre UV Index.
UV Risk Categories
As summer gives way to spring, September in Porto Alegre greets residents with a gentle shift in sunlight, offering a modest 228 hours of sunshine. This marks a slight dip from the vibrant 257 hours seen in August, signaling the transition into the warmer months. It’s noteworthy that the sunshine hours begin to rise again in October, where they jump significantly to 274 hours, showcasing the city’s trend of increasingly abundant light as it moves toward the peak of the summer season. Overall, while September may not boast the sunniest disposition, it sets the stage for the brilliance that follows, embodying the cyclical dance of light and warmth that defines the region's climate.
As summer fades and autumn approaches, Porto Alegre experiences a noticeable shift in sunny weather. In September, the likelihood of enjoying clear skies dips to 30%, marking it as one of the less sunny months of the year. This trend follows a somewhat erratic pattern where the sun shines more generously during mid-year, particularly in July with a peak of 60%. However, as spring begins to emerge, residents can look forward to a gradual increase in sunshine, with October's sun chances climbing back up to 48%. Overall, while September may present a cloudier outlook, the month serves as a transitional phase hinting at sunnier days ahead.
In September, Porto Alegre enjoys a harmonious 11 hours of daylight, marking a subtle transition as the days begin to lengthen after the winter months. This reflects a slight increase from the 10 hours experienced during the colder season of June to August, signaling the approach of spring. Following the gradual decrease of daylight from the peak in January and February, where daylight stretches to a generous 13 hours, the city is now poised to embrace even more sunlight as it heads into October, which promises 12 hours. This shift not only brings a warmer ambiance but also sets the stage for vibrant outdoor activities as the region awakens with the changing season.
As September arrives in Porto Alegre, a noticeable shift in the wind patterns begins to unfold. With an average wind speed of 3.3 m/s (7 mph), September shows a refreshing increase compared to the more subdued winds of the previous months. This marks a subtle yet invigorating transition into spring, setting the stage for the breezy conditions to come. Interestingly, the winds during this month mirror those of October, suggesting a consistent climate as the city bids farewell to winter. Following September, the wind speeds continue to gain momentum throughout the season, climbing to 3.4 m/s (8 mph) in November and reaching 3.7 m/s (8 mph) by December, indicating a trend of increasing vigor as the warmer months beckon. This rise in wind speeds not only enhances the charm of Porto Alegre's outdoor life but also reflects the city's dynamic climate as it awakens from winter's embrace.
Weather in Porto Alegre varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Porto Alegre, focusing on differences in temperature, rainfall, humidity, and UV levels.
In comparing the weather between September and January, we see some notable differences. September experiences cooler temperatures with a minimum of 7°C (45°F) and an average of 18°C (65°F), while January boasts warmer conditions, with a minimum of 15°C (58°F) and an average of 26°C (79°F). Additionally, September is characterized by higher maximum temperatures, reaching up to 36°C (96°F), in contrast to January's peak of 39°C (103°F). Precipitation levels indicate that September is wetter, with 155 mm (6.1 in) over 12 days, compared to January's 93 mm (3.7 in) over the same number of days. Humidity is slightly higher in September at 84%, while January has a more comfortable level at 77%. For more details, you can check out Porto Alegre weather in January.
September and February present distinct weather variations, with September typically experiencing cooler temperatures and higher precipitation. In September, temperatures range from a minimum of 7°C (45°F) to a maximum of 36°C (96°F), with an average of 18°C (65°F) and about 155 mm (6.1 in) of rain over 12 days, resulting in a humidity of 84%. Conversely, February features milder nights, with minimum temperatures of 14°C (58°F) and warmer daytime highs peaking at 38°C (100°F), averaging 25°C (77°F). It has slightly less rainfall at 112 mm (4.4 in) across 11 days, accompanied by a lower humidity of 79%. For a detailed look at February's climate, you can explore Porto Alegre weather in February.
In comparing the weather of September and March, one can observe notable differences. September sees a wider temperature range, with minimums around 7°C (45°F) and maximums peaking at 36°C (96°F), while March has a higher minimum temperature of 13°C (56°F) and a maximum reaching 38°C (100°F). Despite March being warmer on average, it has less precipitation, totaling 109 mm (4.3 in) compared to September's 155 mm (6.1 in), although both months experience rain for about 12 days. Humidity levels are slightly higher in September at 84%, compared to March's 79%, making September feel more humid overall. For more detailed climate information, you can refer to Porto Alegre weather in March.
When comparing the weather in September and April, we see notable differences in temperature and precipitation. September typically experiences a wider temperature range, with minimums around 7°C (45°F) and maximums reaching up to 36°C (96°F), while the average temperature is 18°C (65°F). In contrast, April’s temperatures are generally milder, with a minimum of 8°C (47°F) and a maximum of 34°C (93°F), yielding a more comfortable average of 21°C (71°F). Furthermore, September is characterized by higher precipitation levels at 155 mm (6.1 in) over about 12 days, compared to April's more manageable 73 mm (2.9 in) over just 8 days. Humidity is relatively similar in both months, with September slightly higher at 84% compared to April's 82%. For more detailed information, you can check Porto Alegre weather in April.
September and May both present mild temperatures, yet each month has its unique characteristics. In September, temperatures can range from a cool 7°C (45°F) at night to a warm 36°C (96°F) during the day, with an average of 18°C (65°F). On the other hand, May typically sees slightly cooler temperatures, with a minimum of 5°C (41°F) and a maximum of 32°C (90°F), averaging around 17°C (63°F). Precipitation levels in both months are comparable, with September receiving 155 mm (6.1 in) of rainfall over 12 days, while May sees 153 mm (6.0 in) over just 10 days. Humidity levels are also high, peaking at 84% in September and slightly higher at 87% in May. For more detailed information, you can check Porto Alegre weather in May.
In comparing the weather between September and June, September generally exhibits a wider temperature range, with a minimum of 7°C (45°F) and a maximum that can heat up to 36°C (96°F), resulting in an average temperature of 18°C (65°F). In contrast, June has slightly cooler temperatures, with a minimum of 3°C (38°F) and a maximum of 31°C (88°F), leading to an average of 16°C (60°F). September also sees more precipitation, with 155 mm (6.1 in) over 12 days, compared to June's 113 mm (4.4 in) over just 9 days. Both months experience high humidity, but September's humidity level at 84% is slightly higher than June’s 85%. For more detailed information, check out Porto Alegre weather in June.
When comparing the weather in September to that of July, it's clear that September experiences a broader range of temperatures, with a minimum of 7°C (45°F) and a maximum of 36°C (96°F), compared to July's milder temperatures, which range from 2°C (35°F) to 30°C (87°F). Additionally, September sees higher average temperatures, around 18°C (65°F), while July's average is only 14°C (58°F). Precipitation is more frequent in September, with rain occurring on 12 days and totaling 155 mm (6.1 in), in contrast to July's 8 days of rain and 122 mm (4.8 in). Both months have similar humidity levels, with September at 84% and July at 82%. For those interested in specific details about July weather, you can check Porto Alegre weather in July.
September experiences warmer overall temperatures compared to August, with average temperatures rising from 16°C (61°F) in August to 18°C (65°F) in September. The minimum temperature also increases slightly, from 3°C (38°F) in August to 7°C (45°F) in September, while the maximum temperature can reach as high as 36°C (96°F) in September, compared to 34°C (94°F) in August. Additionally, September sees a significant increase in precipitation, with 155 mm (6.1 in) falling over 12 days, compared to just 70 mm (2.8 in) over 8 days in August. However, both months maintain a relatively high humidity level, with September's humidity slightly higher at 84% compared to 81% in August. For more detailed insights into August's climate, you can check Porto Alegre weather in August.
September and October in Porto Alegre showcase a gradual transition in weather. September typically has a minimum temperature of 7°C (45°F) and an average of 18°C (65°F), with a maximum reaching 36°C (96°F). This month experiences significant rainfall, with a total of 155 mm (6.1 in) spread over 12 days, leading to a humidity level of 84%. In contrast, October sees slightly warmer temperatures, with a minimum of 9°C (49°F) and an average of 20°C (68°F), peaking at 37°C (100°F). The precipitation decreases marginally to 139 mm (5.5 in) over 13 days, and humidity remains close at 85%. The overall weather becomes more conducive for outdoor activities, making October a pleasant month. For more details, you can refer to Porto Alegre weather in October.
September typically ushers in a noticeable transition in weather, featuring minimum temperatures around 7°C (45°F) and an average of 18°C (65°F). With highs potentially reaching up to 36°C (96°F), it’s a month marked by considerable warmth and humidity at 84%. In contrast, November presents a warmer atmosphere overall, with minimums rising to 12°C (53°F) and an average temperature of 22°C (72°F). The maximum temperatures can peak at 37°C (99°F), while precipitation decreases slightly to 112 mm (4.4 in) over about 10 days, maintaining a humidity level of 82%. For a more detailed look at weather patterns, check out Porto Alegre weather in November.
When comparing the weather between September and December, notable differences emerge. September typically sees lower temperatures, with a minimum of 7°C (45°F) and an average of 18°C (65°F), while December enjoys a milder start at a minimum of 13°C (55°F) and an average of 24°C (76°F). Furthermore, December presents maximum temperatures that can reach up to 38°C (101°F), compared to September’s peak of 36°C (96°F). Although September receives more rainfall, totaling 155 mm (6.1 in) over 12 days, December experiences less precipitation at 80 mm (3.2 in) across just 8 days. Humidity remains consistent at 84% for both months. For more details, you can check Porto Alegre weather in December.
As September unfolds in Porto Alegre, the transition from the cooler winter months to the warmer spring is palpable. This month typically presents a blend of warm days and cool nights, marking a delightful change in climate compared to the chill of the previous months. Although rainfall is common, it does not overshadow the sunshine, contributing to a pleasant mix of humidity and warmth. With an average temperature that climbs steadily yet sometimes dips to cooler blasts, September's character sets the stage for the vibrant life of spring ahead. For a more detailed overview, check out the full information at Porto Alegre Climate.