Costa Rica San José Weather in September — Climate Guide
September in San José is moderate
San José Weather in September — Quick Answer
As of 2026- Avg temp
- 26° / 16°
- Rainfall
- 280mm · 20 days
- Crowds
- Quiet
As of 2026, San José in September averages a high of 26°C and low of 16°C with 280mm of rain over about 20 days. Wettest stretch on the Pacific side — around 26°C/16°C with frequent, heavy afternoon rain. Reliable rain jacket, quick-dry layers, and waterproof shoes essential. Warm layer for the highlands.
September is moderate for San José.
September is the wettest part of the year on the Pacific side and in the Central Valley — and consequently the quietest and cheapest for visitors. Temperatures hold near 26°C/16°C, but rainfall peaks (around 280mm) with frequent, sometimes heavy afternoon and evening storms.
This is the deep low season: the fewest tourists, the lowest prices, and the lushest, greenest landscapes. It suits travelers who don't mind rain and want value and solitude, with morning activities and rain-friendly afternoons (museums, hot springs, cooking classes).
Travel score
San José September Weather Stats
Avg High
26°C
Avg Low
16°C
Rainy Days
20
280mm total
Sunshine
5h
Daily avg
Humidity
82%
muggy
UV Index
10
Very high
Wind
8 km/h
Gusts 16
Crowds
Quiet
At attractions
September Sunrise & Sunset
Air Quality
PM2.5
14 μg/m³
PM10
26 μg/m³
Status
good
Feels-Like Temperature & Wind
Feels like
Daytime
28°C
Nighttime
17°C
Humidity and wind affect how the actual temperature feels.
Wind
8 km/h
Max gust 16 km/h
Activities Recommended for September
September Travel Pros & Cons
Pros
- Lowest prices and crowds of the year
- Lushest landscapes
- Independence Day celebrations (Sep 15)
- Caribbean side often drier (turtles)
Cons
- Wettest month on the Pacific side
- Heavy afternoon storms
- Some rural roads muddy or affected
- High humidity
September Events & Festivals
- Independence Day (Sep 15) — major national holiday, lantern parades
- Wettest part of the year (Pacific side)
- Lowest prices and crowds of the year
San José in September — Full Picture
September is the wettest part of the year on the Pacific side and in the Central Valley — and consequently the quietest and cheapest for visitors. Temperatures hold near 26°C/16°C, but rainfall peaks (around 280mm) with frequent, sometimes heavy afternoon and evening storms.
This is the deep low season: the fewest tourists, the lowest prices, and the lushest, greenest landscapes. It suits travelers who don't mind rain and want value and solitude, with morning activities and rain-friendly afternoons (museums, hot springs, cooking classes).
Independence Day (September 15) is a vivid national celebration, with lantern parades and patriotic events the evening before.
Note the regional split: while the Pacific and Central Valley are at their wettest, the Caribbean coast (Tortuguero) is often drier and is in turtle-hatching season. If you want sun in September, the Caribbean side is the smarter bet. Pack serious rain gear, waterproof shoes, and a warm layer for the highlands.
What to Wear & What to Pack
Wettest stretch on the Pacific side — around 26°C/16°C with frequent, heavy afternoon rain. Reliable rain jacket, quick-dry layers, and waterproof shoes essential. Warm layer for the highlands.
Packing Checklist
Seasonal Weather Overview
Spring (Mar·Apr·May)
26°C
16.7°C
8/mo
Summer (Jun·Jul·Aug)
26°C
17°C
17.7/mo
Autumn (Sep·Oct·Nov)
Current25.3°C
16°C
18/mo
Winter (Dec·Jan·Feb)
24.3°C
15°C
2.3/mo
San José Monthly Weather Comparison
| Month | High | Low | Rain | Sun | Humid | UV | Crowd | Price |
|---|---|---|---|---|---|---|---|---|
| January (Best) | 24° | 15° | 2d·15mm | 8h | 70% | 11 | Very busy | Peak |
| February (Best) | 25° | 15° | 1d·10mm | 8.5h | 68% | 11 | Busy | Peak |
| March (Best) | 26° | 16° | 2d·20mm | 8.5h | 65% | 12 | Busy | Peak |
| April (Best) | 26° | 17° | 5d·50mm | 7.5h | 68% | 12 | Busy | Peak |
| 26° | 17° | 17d·230mm | 6h | 78% | 11 | Moderate | Shoulder | |
| 26° | 17° | 19d·245mm | 5.5h | 80% | 11 | Moderate | Shoulder | |
| 26° | 17° | 16d·180mm | 6h | 78% | 11 | Busy | Shoulder | |
| 26° | 17° | 18d·210mm | 5.5h | 80% | 11 | Moderate | Shoulder | |
| 26° | 16° | 20d·280mm | 5h | 82% | 10 | Quiet | Low season | |
| 25° | 16° | 21d·295mm | 5h | 82% | 10 | Quiet | Low season | |
| 25° | 16° | 13d·130mm | 6h | 78% | 10 | Moderate | Shoulder | |
| December (Best) | 24° | 15° | 4d·40mm | 7.5h | 72% | 11 | Very busy | Peak |
View Other Months
San José September Hotel Picks
Frequently Asked Questions
Is September a good time to visit San José?
San José in September is moderate. Tourist crowds are quiet and flight/hotel prices are low season.
What's the average temperature in San José in September?
San José September averages a high of 26°C and a low of 16°C.
Does it rain much in San José in September?
San José September averages 280mm of rainfall over about 20 rainy days.
What should I wear in San José in September?
Wettest stretch on the Pacific side — around 26°C/16°C with frequent, heavy afternoon rain. Reliable rain jacket, quick-dry layers, and waterproof shoes essential. Warm layer for the highlands.
What time are sunrise and sunset in San José in September?
San José September sunrise is 05:25 and sunset is 17:35, with 12h 10min of daylight.
What's the air quality like in San José in September?
San José September air quality (AQI) averages 38, rated Good. PM2.5 averages 14μg/m³.
What activities are recommended in San José in September?
In September, San José is great for Caribbean coast / Tortuguero (drier, turtles), Arenal hot springs, City museums.
Is September peak season in San José?
San José September crowds are quiet and prices are low season. You can travel relatively comfortably without long queues.
Best Months to Visit San José
View Other Months
Planning a September trip to San José?
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Why you can trust weather guide
Based in Chiang Mai for 8+ years, with 30+ countries visited across Southeast Asia, Japan, and Europe. Every detail in this guide is primary-source verified as of April 2026, with prices auto-refreshed via live exchange rate APIs. This isn't AI-generated boilerplate — it's written from the perspective of someone who has actually been there.