Last updated: August 21, 2025
Nestled along the picturesque coastline, Niterói, Brazil experiences a dynamic September, where temperatures soar to a maximum of 34°C (94°F), offering warm days alongside a tranquil average of 23°C (74°F). As the season transitions, expect cooler nights with temperatures dropping to a minimum of 17°C (63°F). With humidity averaging 68% and precipitation totaling 48 mm (1.9 in) over 8 days, occasional showers refresh the vibrant landscape, contributing to the lush, green surroundings and enhancing the allure of this coastal gem. Embrace the unique blend of warmth and refreshing tropical rains that characterize Niterói's September weather.
In September, Niteroi, Brazil, begins to transition into warmer weather, with temperatures reflecting a pleasant shift. The minimum temperature rises to 17°C (63°F), offering a comforting start to the day, while the average temperature settles at a cozy 23°C (74°F). As the month progresses, the maximum temperature can soar to 34°C (94°F), reminiscent of the summer heat that follows. Compared to the cooler months of July and August, this notable increase indicates the approaching summer season. September's delightful mix of mild mornings and warm afternoons makes it an ideal time for outdoor activities, inviting both locals and tourists to enjoy the vibrant atmosphere of Niteroi.
In September, Niteroi experiences a noticeable decline in precipitation, with a total of 48 mm (1.9 in) of rain over 8 days. This reduction follows a series of wetter months, including March and February, which bring heavier downpours, and marks a shift as the dry season approaches. The decrease in rainfall is evident when compared to the average of the preceding months, reflecting a trend toward more stable and drier weather as the city gears up for the upcoming summer. This moderate September precipitation offers a welcome reprieve, allowing residents and visitors to enjoy the beautiful landscapes of Niteroi under clearer skies.
In September, Niterói, Brazil, experiences a noticeable shift in humidity, dropping to 68% from the higher levels of previous months. This decline marks the beginning of the more comfortable fall season, easing from the summer's peak dampness. The trend reveals a gradual decrease in humidity from the end of winter, where August recorded 73%, to this more temperate figure. As the months progress toward October, humidity continues its downward trajectory, reaching a low of 61%, enhancing the city's inviting atmosphere and making it an ideal time for outdoor activities. Thus, September serves as a bridge to more pleasant conditions, paving the way for the drier months ahead.
In September, Niteroi experiences a high UV Index of 11, categorized as extreme, which means residents and visitors alike should be vigilant about sun protection, with a burn time of just 10 minutes. This trend of significant UV exposure continues from the preceding winter months, where the UV Index ranged from 6 to 9, but jumps back up to dangerous levels as spring approaches. Notably, the intensity remains high from January through April, with only slight dips during the middle months. As summer looms, it’s crucial to stay informed and protect your skin. For more information on UV intensity throughout the year, visit Niteroi UV Index.
UV Risk Categories
As September unfolds in Niteroi, Brazil, the city enjoys a delightful average of 293 sunshine hours, making it one of the sunniest months of the year. Following a vibrant summer, where January and February boast impressive totals of 270 and 271 hours respectively, the sun begins to cast its warm glow more generously through March, peaking at 309 hours. As the cooler months approach, sunshine remains abundant, with August closing in at 275 hours. September’s embrace of sunny skies signals a transition that reflects the rhythmic dance of seasons, with daylight gradually tapering into October's 281 hours yet still maintaining a radiant warmth. The trend illustrates not only the city's charm but the consistent allure of Niteroi's sun-kissed days as the year progresses.
As September rolls into Niterói, Brazil, the chance of sunny weather sits at a moderate 50%. This marks a slight dip from the peak months of July and August, where sunny days enjoyed a robust 58% and 60% likelihood, respectively. The trend throughout the year indicates a gradual shift from the more sunlit winter months into the mix of spring, with September maintaining a balance between sun and cloud. Looking forward, the probability of sunny days takes a notable downturn in October, plunging to just 20%, making September a prime time to embrace the vibrant coastal beauty of Niterói before the clouds roll in.
In September, Niteroi witnesses a transitional moment where daylight lingers for 11 hours each day, setting the stage for the upcoming shift toward longer days. Following the consistent 10-hour daylight of the winter months from June to August, September marks a gentle ascent in sunlight, hinting at the brighter days of spring and summer ahead. This rhythm of daylight is a reflection of Niteroi's seasonal changes, beginning to embrace the milder sun of October and the lush vitality of November, which both boast 13 hours of daylight. The increasing daylight duration in September not only enhances outdoor activities but also rekindles the vibrant atmosphere of the city as it moves away from the colder months.
As September arrives in Niteroi, Brazil, the winds begin to pick up, averaging a brisk 4.0 m/s (9 mph). This marks a noticeable shift from the lighter breezes of the earlier months, where January and February saw languid winds of 3.4 m/s (8 mph) and 2.3 m/s (5 mph), respectively. As the seasons transition, the steady increase in wind speed suggests a vibrant energy in the air, reaching its peak in October at 4.2 m/s (9 mph). The ascent from the calm of late summer to the invigorating gusts of early fall reflects the region’s dynamic climate, inviting both residents and visitors to embrace the refreshing September air.
Weather in Niteroi varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Niteroi, focusing on differences in temperature, rainfall, humidity, and UV levels.
In September, the weather typically ranges from a minimum of 17°C (63°F) to a maximum of 34°C (94°F), with an average temperature of 23°C (74°F). The month experiences relatively moderate precipitation of 48 mm (1.9 in) across about 8 days, and the humidity sits at 68%. In contrast, January offers warmer temperatures, with a minimum of 21°C (70°F) and an average of 27°C (81°F), reaching the same maximum of 34°C (94°F). However, January is wetter, seeing 91 mm (3.6 in) of rain over 11 days, along with higher humidity at 85%. For a closer look at January conditions, check out Niteroi weather in January.
September and February display distinct weather patterns, with September experiencing milder temperatures that range from a minimum of 17°C (63°F) to a maximum of 34°C (94°F) and average around 23°C (74°F). In contrast, February tends to be warmer, with minimum temperatures of 21°C (71°F) and maximums reaching 35°C (95°F), averaging 27°C (80°F). Precipitation also varies notably; while September sees about 48 mm (1.9 in) of rain over 8 days, February experiences a significant increase to 119 mm (4.7 in) across 15 days, contributing to a higher humidity of 85%. This makes February notably more humid than September. For more detailed information, you can check Niteroi weather in February.
September and March present distinct weather characteristics despite having similar maximum temperatures. In September, the average temperature hovers around 23°C (74°F), with minimums of 17°C (63°F) and a maximum of 34°C (94°F). This month sees relatively lower humidity at 68% and only 48 mm (1.9 in) of precipitation spread over 8 days.
Conversely, March is warmer with an average temperature of 27°C (80°F), a minimum of 20°C (69°F), and a maximum that matches September at 34°C (94°F). However, March experiences significantly higher rainfall, accumulating 138 mm (5.4 in) over 16 days, along with an increase in humidity to 86%. For more detailed insights on the weather in March, you can visit Niteroi weather in March.
When comparing the weather in September and April, notable differences emerge in temperature and precipitation patterns. September typically experiences a milder temperature range, with minimums around 17°C (63°F) and an average of 23°C (74°F), while April tends to be slightly warmer, with minimums starting at 19°C (67°F) and an average of 25°C (77°F). Both months can reach a maximum of 34°C (93°F), but April is characterized by higher humidity levels at 83%, compared to September's 68%. Additionally, April sees more rainfall, accumulating 81 mm (3.2 in) over 14 days, versus September's 48 mm (1.9 in) over 8 days. For a detailed look at the April climate in Niteroi, you can check out Niteroi weather in April.
When comparing the weather in September and May, we see some similarities and differences. Both months have an average temperature of 23°C (74°F), but September typically experiences slightly higher maximum temperatures, reaching up to 34°C (94°F) compared to May's 33°C (91°F). Precipitation levels are also different, with May receiving 73 mm (2.9 in) over 10 days, making it wetter than September, which has 48 mm (1.9 in) over 8 days. Additionally, humidity levels are higher in May at 81%, compared to 68% in September, adding to the overall mugginess of the earlier month. For more detailed insights, you can check Niteroi weather in May.
In comparing the weather between September and June, September generally experiences slightly warmer temperatures, with an average of 23°C (74°F) and a maximum of 34°C (94°F), compared to June's average of 22°C (73°F) and maximum of 31°C (89°F). September also has a higher total precipitation of 48 mm (1.9 in) over 8 days, whereas June sees 39 mm (1.5 in) of rain across 9 days. Additionally, the humidity in September is lower at 68%, compared to the more humid June, which has a humidity level of 80%. For more detailed insights, visit Niteroi weather in June.
In comparing the weather between July and September, September tends to be slightly warmer with average temperatures reaching 23°C (74°F) compared to July's average of 21°C (71°F). While both months experience relatively low precipitation, September sees a bit more rainfall, with 48 mm (1.9 in) over 8 days, while July has 35 mm (1.4 in) spread over 6 days. Additionally, humidity levels are higher in July at 76%, compared to September’s 68%. For more detailed information on the July weather, you can check Niteroi weather in July.
In comparing the weather between September and August, September experiences slightly warmer temperatures, with a minimum of 17°C (63°F) and an average of 23°C (74°F), rising to a maximum of 34°C (94°F). In contrast, August has cooler temperatures, ranging from a minimum of 14°C (58°F) to a maximum of 32°C (90°F), and an average of 21°C (71°F). Additionally, September is drier with only 48 mm (1.9 in) of precipitation over 8 days, compared to August's 68 mm (2.7 in) over 11 days, although humidity remains relatively high in both months at 68% for September and 73% for August. For more details, you can check Niteroi weather in August.
September and October showcase a noticeable transition in weather patterns. In September, the temperatures range from a minimum of 17°C (63°F) to a maximum of 34°C (94°F), averaging around 23°C (74°F). This month sees about 48 mm (1.9 in) of precipitation over 8 days, with humidity levels at 68%.
In contrast, October brings slightly warmer conditions, with temperatures varying from 17°C (63°F) to a peak of 36°C (97°F), averaging 24°C (75°F). However, it also experiences increased rainfall, totaling 86 mm (3.4 in) over 14 days, accompanied by a decrease in humidity to 61%. For a detailed look at what to expect, check out Niteroi weather in October.
In comparing the weather between September and November, we observe some notable differences. September tends to have slightly cooler temperatures, with minimums around 17°C (63°F) and averages of 23°C (74°F), while November sees a marginal rise in the minimum temperature to 18°C (64°F) and an average of 24°C (75°F). Both months experience maximum temperatures reaching up to 34°C (94°F), demonstrating consistent heat. However, November is significantly wetter, receiving about 115 mm (4.5 in) of precipitation over 16 days, compared to September's 48 mm (1.9 in) over just 8 days. The humidity also rises slightly from September's 68% to November's 72%, contributing to a more tropical feel as the year comes to a close. For more detailed information about November weather, you can visit Niteroi weather in November.
In September, the weather features a minimum temperature of 17°C (63°F) and averages around 23°C (74°F), peaking at a maximum of 34°C (94°F). The month sees a moderate amount of precipitation at 48 mm (1.9 in) over about 8 days, along with a humidity level of 68%. In contrast, December tends to be slightly warmer, with minimum temperatures at 19°C (67°F) and average temperatures reaching 25°C (78°F), while maximums hover around 33°C (92°F). However, December experiences significantly higher rainfall, with 121 mm (4.8 in) spread across 15 days, resulting in a humidity level of 75%. For a detailed look at December weather in Niteroi, you can check this link: Niteroi weather in December.
As September unfolds in Niteroi, the weather presents a delightful blend of warmth and humidity, making it a notable transition month. With maximum temperatures reaching a comfortable 34°C (94°F) and average temperatures settling around 23°C (74°F), it's an appealing time for outdoor enthusiasts. Unlike the wetter summer months, September sees a significant drop in precipitation, with just 48 mm (1.9 in) of rain over about 8 days, providing ample opportunities to enjoy the sun. The 68% humidity adds a tropical flair, reminding visitors that the allure of coastal life is ever-present. For those interested in exploring the unique climate of this beautiful region throughout the year, you can find more information at Niteroi Climate.