Last updated: August 31, 2025
September in San Juan, Puerto Rico offers a tropical climate characterized by warm temperatures and significant rainfall. With maximum temperatures reaching 32°C (90°F) and an average of 28°C (82°F), the weather remains quite inviting despite the humidity averaging around 79%. Visitors can expect frequent showers, as 173 mm (6.8 in) of precipitation typically falls over 23 days throughout the month. While the rain may lead to occasional disruption, the lush landscapes and vibrant atmosphere make September a unique time to experience the island's natural beauty.
In San Juan, Puerto Rico, September continues the warm embrace of summer, with temperatures lingering between a minimum of 24°C (76°F) and a maximum of 32°C (90°F). The average temperature during this month settles at a comfortable 28°C (82°F), reflecting a trend of consistent warmth that characterizes the late summer season. As the month progresses, you’ll notice that the nights remain balmy, inviting evenings spent outdoors. Although September is part of the hurricane season, the heat combined with the vibrant local culture makes for an enticing time to explore the city's rich history and stunning coastline.
September marks a significant peak in precipitation for San Juan, Puerto Rico, as it receives an impressive 173 mm (6.8 in) of rain over 23 days, making it the wettest month of the year. This deluge follows an already increasing trend seen from the previous months, with August accumulating 99 mm (3.9 in) and July reaching 87 mm (3.4 in). The sustained rainfall during September often results from tropical weather patterns, indicating the onset of the Atlantic hurricane season. As the skies open up, the lush landscape flourishes, offering a vibrant contrast to the sun-soaked summers, while residents prepare for the showers that serve as both a blessing for the environment and a challenge for daily life.
September in San Juan, Puerto Rico, sees humidity levels averaging 79%, making it a lush and tropical month. Following the peak of 80% in both July and August, humidity slightly decreases in September, yet remains comfortably high, contributing to the island's vibrant flora and inviting atmosphere. This trend of elevated humidity is typical for the region as the summer months transition into the fall, with only a modest dip in October to 78%. Overall, the consistent humidity throughout these months paints a picture of a warm and humid tropical climate, perfect for enjoying San Juan's lush landscapes and vibrant culture.
In September, San Juan, Puerto Rico, continues to experience a notably high UV Index of 13, classified as extreme with a burn time of just 10 minutes. This trend mirrors the intensifying sunlight seen in the months leading up to September, where the UV Index peaked at 14 in May. As summer transitions into fall, the UV levels remain consistent, emphasizing the importance of sun protection during this period. While the UV Index begins to taper off slightly towards the end of the year, September's high readings remind residents and visitors alike to stay diligent against the sun's rays. For detailed UV insights, check out San Juan UV Index.
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As summer gently transitions to fall, September in San Juan, Puerto Rico, offers a splendid mix of sunshine and warmth, with 313 hours of glorious daylight. This month showcases a slight dip compared to the peak sunshine months of May and June, which basked in an impressive 356 and 343 hours, respectively. However, September's sunshine still remains abundant, allowing locals and visitors alike to embrace the vibrant spirit of the island. Following the sun-drenched days of mid-summer, this transitional month reflects a balanced climate, perfect for enjoying San Juan's beautiful beaches and rich culture while heralding the return of cozy autumn vibes.
In San Juan, Puerto Rico, the likelihood of sunny weather in September shows a modest 48% chance of sunshine, positioning it towards the lower end of the spectrum for the year. While this percentage is slightly below the annual average, it aligns closely with the sunniest months of November (61%) and December (63%), suggesting a gradual improvement in weather as the year progresses. Contrasting the rainy peaks of mid-summer—June (24%), July (43%), and August (41%)—September provides a transitional phase, often offering a balance of sun and occasional showers. As autumn approaches, visitors can still hope for pleasant weather, with the sun making a heartening comeback in the coming months.
In September, San Juan, Puerto Rico, experiences a comfortable 12 hours of daylight, maintaining a steady rhythm that characterizes the late summer months. As we transition from the sun-soaked days of July and August, which boast longer daylight hours of 13 hours, September marks a subtle shift toward shorter days, yet still offers ample sunlight for outdoor activities. This transition hints at the approaching fall, as daylight gradually decreases to 11 hours by October and remains consistent through the winter months. Overall, September stands out as a perfect blend of summer's warmth and the gentle onset of autumn, making it an ideal time for exploration in this vibrant coastal city.
In September, the winds of San Juan, Puerto Rico begin to mellow, with an average wind speed of just 3.2 m/s (7 mph), making it one of the calmest months of the year. As summer transitions into fall, the gusty breezes that characterized the previous months—reaching their peak in July at 5.3 m/s (12 mph)—start to withdraw. This decline in wind speed is a stark contrast to the more robust currents experienced earlier, with average speeds averaging around 4.5 m/s (10 mph) from May to August. As the month unfolds, the tranquil atmosphere fosters a serene environment, inviting both locals and visitors to enjoy San Juan's stunning coastal vistas without the distraction of gusty winds.
Weather in San Juan varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Juan, focusing on differences in temperature, rainfall, humidity, and UV levels.
September and January present contrasting weather patterns. In September, temperatures range from a minimum of 24°C (76°F) to a maximum of 32°C (90°F), with an average of 28°C (82°F). This month typically experiences significant rainfall, totaling 173 mm (6.8 in) over 23 days, and high humidity at 79%. In contrast, January brings milder temperatures, with a minimum of 21°C (69°F) and a maximum of 29°C (85°F), averaging 25°C (77°F). Rainfall is considerably lower in January, at 38 mm (1.5 in) over 12 days, accompanied by a slightly lower humidity of 76%. For a more detailed look at January conditions, visit San Juan weather in January.
In comparing the weather patterns of September and February, September tends to be warmer and much wetter. With average temperatures ranging from a minimum of 24°C (76°F) to a maximum of 32°C (90°F), it presents a more humid atmosphere, featuring an average humidity of 79% and significant rainfall totaling 173 mm (6.8 in) over about 23 days. In contrast, February offers milder temperatures, with a low of 21°C (70°F) and a high of 29°C (85°F), alongside a much drier climate, receiving only 43 mm (1.7 in) of precipitation over 12 days and slightly less humidity at 75%. For more details, you can check out San Juan weather in February.
In comparing the weather of September and March, September tends to be warmer and wetter. The average temperature in September is 28°C (82°F), with highs reaching up to 32°C (90°F), while March sees a cooler average of 25°C (77°F) with maximum temperatures of 30°C (86°F). Additionally, September experiences significant precipitation, with 173 mm (6.8 in) spread over 23 days, compared to March's milder 67 mm (2.6 in) over 14 days. Humidity levels are also slightly higher in September at 79%, as opposed to 74% in March. For more detailed information, visit San Juan weather in March.
When comparing the weather in September and April, September tends to be warmer and wetter. In September, temperatures range from a minimum of 24°C (76°F) to a maximum of 32°C (90°F), with an average of 28°C (82°F). The month is marked by significant rainfall, accumulating 173 mm (6.8 in) over 23 days, accompanied by a high humidity level of 79%. In contrast, April boasts milder conditions, with temperatures ranging from a minimum of 22°C (71°F) to a maximum of 31°C (88°F) and an average of 26°C (78°F). It experiences considerably less rainfall, totaling only 56 mm (2.2 in) over just 10 days, and a slightly lower humidity of 75%. For more details on the weather in April, you can check San Juan weather in April.
When comparing the weather in September and May, September tends to be hotter and wetter. The average temperature in September reaches up to 28°C (82°F) with highs of 32°C (90°F), slightly warmer than May's average of 27°C (80°F). September also experiences significantly more rainfall, with 173 mm (6.8 in) over 23 days, compared to May's 64 mm (2.5 in) over 13 days. Additionally, humidity levels are slightly higher in September at 79%, versus 75% in May. For more detailed information, you can check out San Juan weather in May.
In comparing the weather between September and June, we observe some distinct differences. Both months feature warm temperatures, with September's average temperature slightly higher at 28°C (82°F) compared to June's 27°C (81°F). The minimum temperatures remain consistent at around 24°C (76°F), and both months can peak at a steamy 32°C (90°F). However, September experiences significantly higher rainfall, with 173 mm (6.8 in) spread over 23 days, while June has only 68 mm (2.7 in) over 15 days. Additionally, humidity levels are comparable, with September at 79% and June slightly lower at 77%. For more detailed weather insights, check out San Juan weather in June.
In comparing the weather between September and July, we notice that both months share similar temperature ranges, with minimums of 24°C (76°F), average temperatures of 28°C (82°F), and maximums reaching 32°C (90°F). However, September is notably wetter, with 173 mm (6.8 in) of precipitation over 23 days, compared to July's 87 mm (3.4 in) over 18 days. Additionally, humidity levels remain fairly consistent, slightly higher in September at 79% compared to July's 80%. For more detailed information, you can check San Juan weather in July.
In comparing the weather patterns of September and August, we observe that both months exhibit similar temperature ranges, with minimums at 24°C (76°F), average highs at 28°C (82°F), and maximums peaking at 32°C (90°F). However, September is notably wetter, recording 173 mm (6.8 in) of precipitation over 23 days, compared to August's 99 mm (3.9 in) across 18 days. Humidity levels are slightly lower in August at 80%, while September maintains a high humidity level of 79%. This increase in rainfall and slightly altered humidity may impact outdoor activities throughout the month of September. For more details, you can read about it in San Juan weather in August.
In comparing the weather conditions of September and October, we notice several similarities and a few distinctions. Both months feature a minimum temperature of around 24°C (76°F), with September having a slightly warmer average of 28°C (82°F) compared to October's average of 27°C (81°F). Maximum temperatures remain constant at 32°C (90°F) in September and 32°C (89°F) in October. Precipitation also decreases from September's 173 mm (6.8 in) over 23 days to October's 145 mm (5.7 in) across 22 days, reflecting a slight reduction in rain. Humidity remains fairly consistent, hovering around 79% in September and dropping slightly to 78% in October. For more detailed information, you can check out San Juan weather in October.
In September, the weather tends to be warmer and more humid, with average temperatures reaching 28°C (82°F) and a maximum of 32°C (90°F). This month experiences substantial rainfall, with 173 mm (6.8 in) over 23 days. In contrast, November sees slightly cooler temperatures, averaging 26°C (80°F) and peaking at 31°C (87°F), alongside reduced precipitation of 106 mm (4.2 in) spread over 16 days. The humidity remains high in both months, with September at 79% and November at 78%. For more detailed information, you can explore San Juan weather in November.
In September, the weather tends to be warmer and more humid, with average temperatures peaking at 28°C (82°F) and frequent rainfall totaling 173 mm (6.8 in) over 23 days. The humidity is relatively high at 79%, contributing to a tropical feel. In contrast, December experiences cooler temperatures, with an average of 26°C (78°F), and significantly less precipitation at 51 mm (2.0 in) spread over 16 days. The humidity also decreases slightly to 76%, making December a more comfortable month overall. For more detailed information about the weather in December, you can check San Juan weather in December.
As September rolls in, San Juan experiences a notable shift in weather conditions. This month is characterized by warm temperatures, typically averaging around 28°C (82°F), with peaks reaching the 32°C (90°F) mark. However, what sets September apart is the increased rainfall, with nearly twenty-three days of precipitation contributing to a total of 173 mm (6.8 in), making it one of the wettest months of the year. Combined with a humidity level hovering around 79%, the air feels notably thicker, creating a tropical ambiance that can be both invigorating and challenging. To find out more about how September weather fits into the broader context of San Juan's climate, visit San Juan Climate.