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Alajuela Weather in September
September in Alajuela averages 25°C (77°F) during the day and 17°C (63°F) at night. September is part of the rainy season, with around 433 mm (17 in) of rainfall and frequent showers.
Rainfall in Alajuela in September
As part of the rainy season, Alajuela sees around 24 days of rain in September, with an average of 433 mm (17 in). Showers during the rainy season tend to be heavy and can come down intensely. An umbrella is often not enough, so a poncho or waterproof jacket is a better choice.
Temperature in Alajuela in September
Daytime temperatures in Alajuela reach 25°C (77°F) in September, dropping to 17°C (63°F) at night. The days can feel warmer than the evenings, so packing for both parts of the day is a good idea. With lows of 17°C (63°F), nights are cool. If you're out after dark, an extra layer will keep you comfortable. The cooler air at night is also great for getting a good rest.
Sunshine in Alajuela in September
The city usually sees around 149 hours of sunlight, indicating a moderately sunny period (despite it being part of rainy season).September in Alajuela can still be great, but if you prefer pleasant temperatures along with dry and sunny conditions, our weather planner can help you explore other options in the world.
Alajuela Temperature in September
Min Temperature
17°C (63°F)
Max Temperature
25°C (77°F)
Chance of Rain
80%
Precipitation
433 mm (17 in)
Rainy days
24 days
Humidity
85% *
Sunshine
149 hours *
Percentage Sunshine
*
* Data from: San José, Costa Rica (17 KM, 11 Miles).
Alajuela Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Alajuela - and find the best time to visit.
Daily Historical Temperatures
44-year average (1976-2025)
Based on our historical records, temperatures in Alajuela typically stay consistent throughout September, with daily highs averaging around 25°C (77°F). Nights are pleasant, with lows around 19°C (66°F).
Average temperatures in September
Daily Historical Precipitation
44-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather records for Alajuela in September
Browse day-by-day weather records for Alajuela spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Alajuela historical weather extremes in September
Based on 30 years of weather observations in Alajuela between 1996 and 2026, these are the recorded extremes.
- The warmest day in September was on September 3, 1998, with a maximum of 32°C (90°F).
- On September 29, 2010, Alajuela saw its coldest September day with temperatures maxing out at 21°C (70°F).
- The lowest overnight temperature recorded in September was 11°C (52°F) (September 29, 2010).
- The wettest September day on record brought 170 mm (6.7 in) of precipitation to Alajuela (September 27, 2019).
Best Places in Costa Rica in September
Find out more about the weather in Costa Rica and which places have the best travel conditions in this month. See all of Costa Rica in September →
perfect weather
pleasant
tolerable
unpleasant
poor
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).
What to Wear in Alajuela in September
Warm weather calls for comfortable, breathable clothing in September. Cotton t-shirts, shorts, light dresses, and sandals are perfect. You might still want a light layer for evenings or air-conditioned places (for example buses). Also bring a poncho, it will rain a lot! Waterproof everything you can. Bring sunglasses since you'll have some sunny periods throughout the month
What To Do in Alajuela in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
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Swimming7/10 -
Cycling7/10 -
Walking7/10 -
Camping6/10 -
Outdoor sports7/10
Alajuela 3-Day Forecast
More climate data for Alajuela
Temperature Rainfall Sunshine Humidity
See the full Alajuela climate overview or explore weather in Costa Rica.
Popular in September
Where to go in September - average daytime high across popular destinations.
Tamarindo
30°C (86°F) Cahuita29°C (84°F) Santa Teresa29°C (84°F) Herradura28°C (82°F) Puerto Viejo de Talamanca29°C (84°F) Fortuna29°C (84°F) Jacó28°C (82°F) San José24°C (75°F) Bucket list
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