Last updated: August 21, 2025
September in San Jose, Costa Rica offers a warm and humid climate, with maximum temperatures reaching up to 29°C (84°F) and averaging around 25°C (78°F). Visitors can expect a mix of overcast skies and rain, as the region experiences significant precipitation of about 272 mm (10.7 in) over 29 rainy days. With humidity levels consistently around 80%, September presents a lush, vibrant landscape, making it a perfect time for those who appreciate the beauty of Costa Rica's rainy season.
In September, San Jose, Costa Rica, continues to bask in mild tropical warmth, with temperatures ranging from a comfortable 22°C (73°F) at night to a pleasant 29°C (84°F) during the day. The month maintains an average temperature of 25°C (78°F), consistent with the preceding months. This trend reflects a transition from the warmer, drier season in earlier months towards an increased chance of rain as September falls within the rainy season. Visitors can expect a mix of sunshine and refreshing rain showers, making it a lush time to appreciate the vibrant landscapes and rich biodiversity that Costa Rica has to offer.
In September, San Jose, Costa Rica, experiences significant rainfall, with an average precipitation of 272 mm (10.7 in) over 29 days. This marks a continued trend from the heavy August showers, reflecting the region's transition into the heart of the wet season. While September's totals are slightly lower than October's peak of 387 mm (15.2 in), the consistency of rain during this month underscores the persistent moisture that characterizes the season. The damp conditions can lead to vibrant landscapes, making the lush greenery of the region particularly stunning. As the rainfall continues to flow into the following months, it highlights the tropical climate's rhythm, offering both challenges and opportunities for the local ecosystem and its inhabitants.
In September, San Jose, Costa Rica experiences a humidity level of 80%, reflecting a trend that begins in the warmer months. As the year progresses, humidity tends to climb, peaking in July at 85% before gradually decreasing in the following months. The consistently high humidity during the rainy season from June through September is indicative of the region's tropical climate, characterized by lush greenery and vibrant ecosystems. While September maintains a high moisture level, it also marks the beginning of a subtle decline as the weather transitions towards October, which sees an average humidity of 79%. This pattern highlights the inherent fluctuations in San Jose's weather, where humidity plays a significant role in shaping the local environment and experience.
In September, San Jose, Costa Rica, continues to experience an extreme UV Index of 13, consistent with the high levels seen throughout the preceding months. This pattern persists from the intense summer UV levels in March, April, May, June, and July, where the Index peaked at 14. September’s UV Index indicates that residents and visitors should remain vigilant, as the risk of harm from unprotected sun exposure is significant, with a minimal burn time remaining at just 10 minutes. This trend emphasizes the need for proper sun safety measures throughout the year, as the UV Index gradually declines towards the end of the year. For more detailed information on solar exposure in the area, check out the San Jose UV Index.
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September in San Jose, Costa Rica, brings a delightful blend of sunshine with 284 hours of radiant daylight, perfectly nestled between the vibrant sun-drenched months of July and August, which boast 312 and 293 hours, respectively. This slight dip is typical as the rainy season progresses, yet it still highlights the consistent brightness of the region compared to the darker months ahead. As the year unfolds, March shines the brightest with an impressive 332 hours, while April and December maintain their charm with 325 and 318 hours of sun. Overall, the sun-soaked days in San Jose offer a captivating preview of the vibrant landscapes and bustling city life that thrives under the warm embrace of its idyllic climate.
In San Jose, Costa Rica, September is not particularly known for its sunny weather, as it boasts a meager 15% chance of sun—one of the lowest probabilities throughout the year. The month follows a trend of diminishing sunshine, typically seen from August's 9% to October's slight recovery at 25%. This pattern highlights the region's rainy season, suggesting that visitors should prepare for frequent showers rather than sunny skies. As the year progresses, the likelihood of sunshine gradually increases, with December offering a robust 42%, making it a more favorable time for those seeking bright days.
In September, San Jose, Costa Rica, enjoys a consistent 12 hours of daylight, continuing the trend established since March. This month marks a transition within the year, as daylight hours begin to stabilize before gradually decreasing in October. From January to February, the duration of daylight remains at 11 hours, reflecting the city's near-equatorial position. As we move into the lush, vibrant months of March through September, the daylight stretches to a comfortable 12 hours, allowing residents and visitors alike to immerse themselves in the natural beauty and outdoor activities that flourish in this vibrant locale. As the year winds down in October, daylight dips once again, returning to the 11-hour mark seen in the early months.
In September, San Jose, Costa Rica experiences a gentle lull in the winds, with average speeds dropping to a modest 3.0 m/s (7 mph), mirroring the calmer breezes of August. This period marks one of the year's quietest phases, offering a serene backdrop as the vibrant greenery of the region continues to thrive. As the month unfolds, the tranquility of the wind contrasts neatly with the more spirited gusts of earlier months like January and March, where speeds reach upwards of 5.6 m/s (12 mph) and 5.7 m/s (13 mph), respectively. This trend highlights a significant seasonal shift, suggesting that September is a time for reflection and leisure, inviting both locals and visitors to savor the peaceful ambiance of the city before the winds pick up again in the coming months.
Weather in San Jose varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Jose, focusing on differences in temperature, rainfall, humidity, and UV levels.
September and January display notable differences in weather patterns. September maintains a warm average temperature of around 25°C (78°F), with daily highs reaching up to 29°C (84°F). However, this month is characterized by high humidity at 80% and significant precipitation of 272 mm (10.7 inches) over 29 days, making it one of the wettest periods of the year. In contrast, January is slightly cooler, with average temperatures at 24°C (75°F) and maximums peaking at 27°C (82°F). It experiences considerably less rainfall, totaling 148 mm (5.8 inches) over 22 days, and exhibits lower humidity at 66%. This shift from the humid and rainy September to the relatively drier and cooler January conditions is a significant transition in the climate. For more detailed insights on how the weather varies during this month, check out San Jose weather in January.
September and February present contrasting weather patterns. In September, temperatures remain mild, with a minimum of 22°C (73°F) and an average of 25°C (78°F), peaking at a maximum of 29°C (84°F). However, this month is marked by significant rainfall, totaling 272 mm (10.7 in) over 29 days, combined with a high humidity level of 80%. In contrast, February experiences slightly cooler temperatures, ranging from a minimum of 20°C (68°F) to an average of 24°C (76°F) and a maximum of 28°C (83°F). This month is much drier, with only 96 mm (3.8 in) of precipitation spread over 20 days and a significantly lower humidity of 64%. For more details on February weather, visit San Jose weather in February.
In comparing the weather of September and March, September is typically warmer with average temperatures ranging from a minimum of 22°C (73°F) to a maximum of 29°C (84°F), while March experiences slightly cooler temperatures, with a minimum of 21°C (69°F) and a maximum of 28°C (83°F). September also sees significantly higher precipitation, with 272 mm (10.7 in) over 29 days, compared to March’s 102 mm (4.0 in) over 23 days. Additionally, the humidity in September is notably higher at 80%, while March has a more moderate humidity level of 63%. For a more detailed look at the weather specifics for March, visit San Jose weather in March.
September and April display notable differences in weather patterns. Both months have similar minimum temperatures, averaging around 22°C (73°F), but April tends to be slightly warmer overall, with an average temperature of 26°C (78°F) compared to September's 25°C (78°F). In terms of maximum temperatures, April peaks at 30°C (87°F), while September reaches a high of 29°C (84°F). Additionally, September is significantly wetter, receiving 272 mm (10.7 in) of precipitation over 29 days, whereas April has a much lighter rainfall of 75 mm (2.9 in) across 19 days. Humidity levels also differ, with September averaging 80% compared to April's 63%. For more detailed information, check out San Jose weather in April.
September and May share similar minimum temperatures, averaging around 22°C (73°F), but May tends to be slightly warmer overall with an average of 26°C (78°F) compared to September's 25°C (78°F). The maximum temperatures are also comparable, with May reaching up to 30°C (85°F) while September peaks at 29°C (84°F). However, September experiences a higher level of precipitation at 272 mm (10.7 in) across 29 days, compared to May's 297 mm (11.7 in) over 28 days. Additionally, the humidity in September is significantly higher at 80%, in contrast to May's more comfortable 63%. For more detailed information, you can visit San Jose weather in May.
In comparing the weather between September and June, both months exhibit similar average temperatures, with September's temperatures ranging from a minimum of 22°C (73°F) to a maximum of 29°C (84°F), while June shows slightly higher minimum temperatures of 23°C (73°F) and a maximum of 29°C (85°F). Precipitation levels are notably higher in June, with 337 mm (13.3 in) over 30 days compared to September's 272 mm (10.7 in) over 29 days. Additionally, September presents a higher humidity level at 80%, compared to June's 74%. For a more detailed look at June’s climate specifics, you can refer to San Jose weather in June.
In comparing the weather between July and September, both months feature similar temperature ranges, with July displaying a slightly lower maximum temperature of 28°C (84°F) compared to September's 29°C (84°F). However, September experiences a marginally higher average temperature of 25°C (78°F) compared to July's 25°C (77°F). Precipitation levels are quite comparable, with September receiving 272 mm (10.7 in) over 29 days, just slightly higher than July's 270 mm (10.6 in) spread across 30 days. Humidity is also higher in July at 85%, while September's humidity sits at 80%. For more detailed insights into the July climate, you can visit San Jose weather in July.
In comparing the weather between September and August, we find that both months share similar temperature ranges, with minimums around 22°C, averages of 25°C, and maximums close to 29°C. However, September experiences slightly less precipitation, with 272 mm compared to August's 286 mm, despite both months featuring a similar number of rainy days (29 in September and 30 in August). Additionally, humidity levels are slightly lower in September at 80% compared to 82% in August, making September just a touch more comfortable. For more detailed information on August weather, you can check San Jose weather in August.
In September, the weather features a warm climate with temperatures ranging from a minimum of 22°C (73°F) to a maximum of 29°C (84°F), accompanied by high humidity levels of 80%. This month experiences significant rainfall, totaling 272 mm (10.7 in) spread over 29 days.
October, while maintaining similar temperatures with a minimum of 22°C (72°F) and a maximum of 28°C (83°F), sees an increase in precipitation, with a total of 387 mm (15.2 in) over 28 days, leading to a slightly lower humidity level of 79%. For a more detailed look at October weather patterns, you can refer to San Jose weather in October. Overall, both months share comparable temperatures, but October is notably wetter.
September and November exhibit similar temperature patterns, with September experiencing an average of 25°C (78°F) and November slightly cooler at 24°C (76°F). Both months feature high nighttime temperatures, with a minimum of 22°C (72°F in November), making the evenings pleasantly warm. However, November sees a slight increase in precipitation, totaling 306 mm (12.0 in) over 28 days compared to September's 272 mm (10.7 in) over 29 days. Humidity remains high and relatively consistent between the two months, with September at 80% and November at 79%. For more detailed information, you can explore San Jose weather in November.
In September, the weather tends to be warmer, with average temperatures ranging from a minimum of 22°C (73°F) to a maximum of 29°C (84°F), while December sees slightly cooler temperatures, with a minimum of 20°C (69°F) and a maximum of 28°C (82°F). Both months experience significant precipitation, but September is particularly wet, receiving 272 mm (10.7 in) of rainfall over 29 days compared to December's 212 mm (8.3 in) over 27 days. Additionally, September's humidity levels are higher at 80%, while in December, humidity drops to a more comfortable 70%. For more details on December's weather, check out San Jose weather in December.
In September, San Jose experiences a unique blend of warm temperatures and high humidity, making it feel quite different from the drier months that precede and follow it. While the average temperature remains pleasant, the city is enveloped in a symphony of rain, with nearly every day contributing to the total precipitation—far exceeding what is typical in the rest of the year. As the lush landscape flourishes under the abundant moisture, visitors can expect a vibrant but occasionally soggy ambiance. For a more comprehensive understanding of the region’s climate, check out San Jose Climate.