Last updated: August 21, 2025
In September, Alajuela, Costa Rica experiences a warm and humid tropical climate, with temperatures ranging from a maximum of 27°C (80°F) to a comfortable average of 20°C (69°F), and a minimum of 15°C (60°F). This month is characterized by significant rainfall, accumulating around 436 mm (17.2 in) over 28 days, contributing to the lush greenery of the region. With humidity levels soaring at 81%, visitors can expect a vibrant, moist atmosphere, perfect for experiencing the natural beauty of this captivating destination.
In September, Alajuela, Costa Rica, experiences a delightful yet moderate climate that mirrors the rainy season's embrace. With nighttime temperatures dipping to a comfortable 15°C (60°F), the days remain pleasantly warm with averages around 20°C (69°F) and highs reaching 27°C (80°F). This month marks a subtle shift, as temperatures begin to stabilize, transitioning from the slightly cooler values of the preceding months. The result is an inviting atmosphere perfect for exploring lush landscapes or savoring the region's rich biodiversity. While September showcases warm days and cooler nights, it also carries the refreshing promise of rain, nourishing the vibrant flora that defines this captivating locale.
September marks one of the wettest months in Alajuela, Costa Rica, with an impressive 436 mm (17.2 in) of rainfall spread over 28 days. This significant precipitation is part of the broader pattern of the rainy season, which begins in earnest from May and peaks in October. In fact, September's rainfall is rivaled only by October, suggesting that the region experiences a cumulative intensity of wet weather as the year progresses. As the lush landscape thrives under the weight of the rains, it becomes clear that September embodies the heart of Costa Rica's vibrant, tropical climate, providing essential moisture to the rich biodiversity that characterizes this stunning locale.
In September, the humidity in Alajuela, Costa Rica, averages a notable 81%, marking a slight decrease from the heightened levels experienced in the preceding months of June (84%), July (85%), and August (82%). This trend reflects a typical pattern in the region, where the rainy season peaks during the middle of the year, leading to increased moisture in the air. As the dry season approaches, September's humidity remains relatively high but hints at a gradual easing, paving the way for more comfortable conditions in the following months like October (80%) and November (80%). Despite the humidity fluctuations, the lush landscapes and vibrant ecosystems of Alajuela thrive, making this period a vibrant time to experience the region's natural beauty.
In September, Alajuela, Costa Rica, continues to experience extreme UV levels, characteristic of the preceding months. With a UV Index of 13, the potential for skin damage remains high, signaling a burn time of just 10 minutes. This month aligns closely with the averages seen from February to August, where consistent UV indices lingered between 13 and 15. As the year progresses into October, the UV Index slightly dips to 14, yet the caution remains the same throughout**. Ensuring proper sun protection is crucial during this period, as the intensity of solar radiation in Alajuela is not to be underestimated. For more information on current conditions, check out Alajuela UV Index.
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September in Alajuela, Costa Rica brings a delightful mix of sunshine, with 230 hours of bright days. This figure marks a noticeable increase from the wetter months of June and July, which recorded only 226 and 209 hours respectively. As the transition from the dry season begins, September offers a balance, nestled between the peak sunny days of March with 329 hours and the gradual decline as the year winds down. Despite being a slightly overcast month compared to the sun-drenched February and March, September’s warmth and lively atmosphere are invigorating, making it an ideal time to explore the rich natural beauty of this Central American paradise.
In Alajuela, Costa Rica, the likelihood of sunny weather in September plummets to a mere 8%, making it one of the cloudiest months of the year. This trend follows a gradual decline in sunshine that begins in April, where the chances drop to 20%, and continues through the wettest months of May, June, and July, all of which linger below 20%. As August arrives, the sun's sightings dwindle even further to just 6%, foreshadowing the gloomy skies of September. While October offers a slight reprieve with a 14% chance of sunshine, the month of September stands out as a notably gray period, perfect for those who enjoy lush landscapes nourished by the rainy season.
In September, Alajuela, Costa Rica, enjoys a consistent 12 hours of daylight, maintaining the trend established over the preceding months. This balance of light allows residents and visitors to fully embrace the vibrant natural beauty of the region, whether it's exploring lush rainforests or engaging in local festivities. Interestingly, the daylight duration shows a shift from the 11 hours seen in January, February, and October, steadily increasing to the more abundant 12 hours experienced from March through September. As the year transitions toward its end, the daylight gradually tapers back, signaling a return to shorter days. This rhythmic cycle of light beautifully reflects the region's tropical climate, making Alajuela a captivating destination year-round.
In September, the winds in Alajuela, Costa Rica are gentle, with an average speed of 1.2 m/s (3 mph), continuing a trend of lighter breezes that began in the earlier summer months. Throughout the year, wind speeds fluctuate, peaking in the cooler months of January to April, where they hover around 2.4 m/s (5 mph) to 1.7 m/s (4 mph). As summer rolls into the rainy season, wind speeds dip to their lowest in August and September, often creating a serene atmosphere perfect for enjoying the lush, green landscapes. As we move into October, the trend persists, with wind speeds remaining low, but a gradual increase is anticipated in the months to follow, once more returning to the refreshing breezes of the drier season.
Weather in Alajuela varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Alajuela, focusing on differences in temperature, rainfall, humidity, and UV levels.
In comparing the weather between September and January, we observe some notable differences. September tends to be quite wet, with an average temperature of 20°C (69°F) and a significant precipitation of 436 mm (17.2 in) spread over 28 days, resulting in high humidity at 81%. In contrast, January offers a more pleasant experience, maintaining a similar average temperature of 20°C (68°F) but with much less rainfall—only 32 mm (1.3 in) over 6 days, leading to a lower humidity of 68%. Therefore, while both months feature similar temperatures, January provides a drier and more comfortable atmosphere. For more specific details, you can check Alajuela weather in January.
September and February both feature mild average temperatures of around 20°C (69°F); however, September tends to be much wetter and more humid. With a minimum temperature of 15°C (60°F) and a maximum of 27°C (80°F), September experiences significant rainfall, measuring 436 mm (17.2 in) over 28 days, resulting in a humidity level of 81%. In contrast, February boasts slightly cooler minimum temperatures at 13°C (56°F) and higher maximums at 28°C (83°F), but it is considerably drier, with only 13 mm (0.5 in) of precipitation over just 3 days, leading to a lower humidity of 68%. For those interested in exploring February weather conditions, more details can be found Alajuela weather in February.
In comparing September and March weather, September tends to be wetter and more humid, with an average temperature around 20°C (69°F) and significant precipitation of 436 mm (17.2 in) over 28 days, resulting in a humidity level of 81%. In contrast, March experiences slightly milder temperatures, with an average of 21°C (70°F) and much lower rainfall of just 15 mm (0.6 in) spread over only 4 days, leading to a more comfortable humidity level of 66%. For more detailed information on the weather patterns in March, you can check this link: Alajuela weather in March.
In comparing the weather of September and April, September presents a cooler climate with average temperatures ranging from 15°C (60°F) to 27°C (80°F), and significantly higher precipitation at 436 mm (17.2 in) over 28 days, resulting in a notably high humidity of 81%. In contrast, April enjoys slightly warmer temperatures, with averages between 15°C (58°F) and 29°C (85°F), and considerably less rainfall at 79 mm (3.1 in) across 16 days, leading to lower humidity levels of 67%. For more detailed insights about April weather, you can visit Alajuela weather in April.
When comparing the weather in September to that of May, one can observe a few notable differences. September typically has slightly lower temperatures, with an average of 20°C (69°F) compared to May's 21°C (70°F). However, September is more humid, with humidity levels around 81%, while May enjoys a fresher 69% humidity. In terms of precipitation, September is wetter, receiving 436 mm (17.2 in) over 28 days, compared to May's 391 mm (15.4 in) spread over 27 days. For more detailed information on the weather in May, you can visit Alajuela weather in May.
September and June share similar temperature ranges, with both months experiencing maximum temperatures around 27°C (81°F). However, September has slightly lower average temperatures of 20°C (69°F), compared to June's average of 21°C (70°F). Precipitation is notably higher in September, with 436 mm (17.2 in) over 28 days, contrasted with June's 351 mm (13.8 in) over 27 days. Additionally, humidity levels are slightly higher in June at 84%, compared to 81% in September, making both months feel quite humid. For more detailed information about June weather, you can refer to Alajuela weather in June.
When comparing the weather in September and July, both months exhibit similar temperature ranges, with average highs reaching 27°C (81°F). However, September tends to be a bit cooler, averaging 20°C (69°F) compared to July's 21°C (69°F). Precipitation is significantly higher in September, totaling 436 mm (17.2 in) over 28 days, whereas July sees only 233 mm (9.2 in) across 26 days. Additionally, September's humidity at 81% is slightly lower than July's 85%, making July feel a bit more muggy. For more details on July weather, you can visit Alajuela weather in July.
In comparing the weather between August and September, we notice some distinct differences. While both months exhibit an average temperature of 20°C (69°F), September tends to have slightly lower minimum and maximum temperatures, with a range from 15°C (60°F) to 27°C (80°F) compared to August's 16°C (60°F) to 28°C (82°F). Additionally, September experiences significantly more precipitation, totaling 436 mm (17.2 in) over 28 days, compared to 331 mm (13.0 in) over 26 days in August. Humidity levels remain similar, with September at 81% and August at 82%. For those interested in exploring August’s climate in detail, refer to Alajuela weather in August.
September and October share similar temperature ranges, with both months featuring a minimum of 15°C (60°F), an average of around 20°C (69°F to 68°F), and a maximum of 27°C (80°F). However, October sees a notable increase in precipitation, totaling 570 mm (22.4 in) over 29 days, compared to September's 436 mm (17.2 in) across 28 days. This slight uptick in rainfall, paired with consistent humidity levels hovering around 80%, makes October feel a bit wetter than September. For more detailed insights about the weather in October, you can check Alajuela weather in October.
September and November exhibit similar temperature patterns, with both months featuring a minimum of 15°C (60°F), an average of around 20°C (68°F-69°F), and a maximum reaching near 27°C (80°F) in September and 26°C (79°F) in November. However, the rainfall contrasts dramatically; September experiences high precipitation levels of 436 mm (17.2 in) over 28 days, while November sees a significant reduction, with only 209 mm (8.2 in) over 19 days. Humidity remains relatively stable, hovering around 81% in September and 80% in November. For more detailed insights, visit Alajuela weather in November.
In September, Alajuela experiences a warmer and more humid climate with average temperatures around 20°C (69°F) and frequent precipitation of 436 mm (17.2 in), spread over 28 days. The humidity is high at 81%, creating a muggy atmosphere. In contrast, December sees a slight decrease in both temperature and humidity, maintaining an average of 20°C (68°F) while having significantly lower rainfall at 63 mm (2.5 in) over just 11 days, contributing to a more comfortable environment. For more details on weather specifics, you can check Alajuela weather in December.
In September, Alajuela experiences a distinctive weather pattern characterized by increased humidity and significant rainfall, setting it apart from other months. With an average temperature of 20°C and frequent precipitation, this month has the highest number of rainy days, making it a lush and vibrant time for nature. The persistent humidity can create a muggy atmosphere, but it also enriches the region's stunning landscapes. For travelers and locals alike, understanding this unique weather dynamic is essential for enjoying the area's natural beauty. For more detailed insights on what to expect throughout the year, check out Alajuela Climate.