San Jose Weather in September

🇨🇷 Costa Rica

30°C

High

23°C

Low

Rain Days

Sunshine

82%

Humidity

North America › 🇨🇷 Costa Rica › San Jose

Updated: March 2026

Is September a Good Time to Visit San Jose?

3/10

Avoid

September is a avoid time to visit San Jose (3/10). Average highs of 30°C and 4 sunshine hours daily make conditions workable, though not exceptional. September suits travellers visiting for indoor culture, food, and architecture rather than outdoor activities. Pack accordingly for 12 potential rain days. October offers a similar profile at lower hotel rates if dates are flexible. The main practical note: San Jose's popular sites are busiest between 10am and 3pm regardless of season. Arriving at opening time or after 4pm makes a significant difference to the experience. Planning tips: most accommodation categories have availability, and last-minute deals are common. The quieter streets and shorter queues can make this a genuinely enjoyable time to visit for the right type of traveller. Budget-conscious visitors will find the best value of the year in this period.

vs August:31°C avg high

Visiting San Jose in September means warm daytime temperatures peaking at 30°C. Factor in 12 potential rainy days and 82% average humidity when planning your daily activities.

30°C

Avg High

23°C

Avg Low

12 days

Rain Days

Sunshine

82%

Humidity

Temperature in San Jose in September

The 7°C day-night temperature range is typical for continental climates: a light jacket in the morning that you shed by midday and need again after sunset. At 82% humidity, the 30°C daytime high feels 2-4°C warmer in practice: quick-dry fabrics and shade-seeking between noon and 3pm are the sensible response. UV index averages 6 this month, classed as moderate. Sunscreen is a sensible precaution for extended outdoor time, particularly at midday. Wind averages 15 km/h, light enough to be refreshing on warm days but noticeable in open coastal areas or elevated viewpoints. In Fahrenheit: 86°F average high, 73°F overnight low. Data sourced from Open-Meteo ERA5 climate reanalysis (1991–2020 normals).

Temperature in September

Monthly Precipitation (mm)

What to Wear in San Jose in September

Morning23°CBefore the day warms up

Afternoon30°CPeak daytime temperature

Evening26°CAfter sunset cools down

Packing for San Jose in September means dressing for 30°C days and 23°C evenings. A lightweight linen or cotton shirt with loose-fit trousers or a sundress handles the 30°C daytime heat. Evening temperatures settle at 23°C, a modest 7°C drop that a light cardigan or denim jacket covers. For footwear, breathable walking sandals work for casual exploration, but closed-toe trainers are better for uneven surfaces in the historic centre. A compact foldable umbrella weighs almost nothing and earns its keep across 12 potential rainy days. At 82% average humidity, quick-dry synthetic or bamboo fabrics dry overnight and stay comfortable longer than cotton.

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Local tip: Layers are more practical than a single heavy garment in San Jose. The day-to-evening temperature shift rewards packing a versatile mid-layer you can add or remove as conditions change.

Events in San Jose in September

September has no major festivals or public holidays in San Jose, which is one of its practical advantages for independent travellers. Attractions run at lower capacity than during peak event periods, queues are shorter, and accommodation is easier to find without needing to book many months in advance. Local restaurants, markets, and transport operate at a relaxed pace, making this an ideal time for visitors who prefer a more authentic, unhurried experience of everyday city life rather than large crowds drawn in by a single major headline event.

What to Pack for San Jose in September

Based on 30°C average highs and 12 rainy days

Light layers for morning and evening
Breathable T-shirts and comfortable trousers
UV-protective sunglasses
Quick-dry travel towel
Anti-chafe balm for long walking days
Moisture-wicking synthetic fabrics for active days
Compact folding umbrella
Waterproof outer layer or packable rain jacket
Quick-dry clothing that recovers fast after a shower
SPF 30+ sunscreen
Comfortable walking shoes (a second pair lets the first air out overnight)
Universal travel adapter
Small day pack for city exploration
Reusable water bottle

Best Activities in San Jose in September

Early morning walk through San Jose's historic market districtBest before 9amTemperatures are still manageable at 26°C before the midday heat builds
Open-air rooftop dining at sunsetFrom 6pm onwardsThe 30°C daytime heat drops noticeably after sunset, making al fresco dining comfortable
Waterfront promenade or harbour walkEarly morning or after 5pmSea breezes cut through the humidity, making coastal routes the most pleasant in heat
Guided cycling tour of the old quarterFirst tour of the day (7-9am)The low-traffic window before tourist crowds and the cooler morning air make this the prime riding slot
Afternoon in a world-class museum or galleryAfternoon (2-5pm)Pairs well with outdoor morning activities and provides a mid-day rest from sightseeing
Coffee-house or traditional cafe culture experienceMid-morning or post-lunchA cultural ritual in this region that rewards slow appreciation regardless of weather
Evening live music, theatre, or opera performanceEvening shows typically at 7-9pmConsistent evening temperatures make getting to and from evening venues comfortable
Visit the main botanical garden or city park at seasonal peakYear-round; best light in morningSeptember brings distinct seasonal changes to public green spaces worth exploring
Seek out chilled local specialities: cold-brew tea, ice desserts, or chilled seafood at street-level stallsAny time; most atmospheric in evening marketsHot-weather street food culture peaks in September, with vendors setting up specifically for warm evenings

Why is San Jose warm in September?

San Jose's September climate is governed by the Inter-Tropical Convergence Zone (ITCZ), which draws moisture-laden trade winds across the region, producing the characteristic wet season rainfall of steamy tropical cities. Daytime heat peaks around 30°C, moderated slightly by afternoon convective showers. Overnight temperatures remain warm at 23°C because the humid air retains heat effectively. Climate data: Open-Meteo ERA5 (1991–2020).

Sunshine Hours

The average number of hours per day with direct sunlight. Calculated from satellite measurements. Days with more than 7 hours of sunshine are ideal for outdoor activities. Under 3 hours means overcast conditions dominate.

UV Index

A scale from 0-11+ measuring ultraviolet radiation intensity. UV 0-2: Minimal risk. UV 3-5: Moderate -- wear sunscreen. UV 6-7: High -- hat and SPF 30+ essential. UV 8-10: Very High -- limit midday exposure. UV 11+: Extreme -- seek shade between 10am-4pm.

Rain Days

A rain day is counted when precipitation exceeds 0.1mm. This threshold captures even light drizzle. Unlike total rainfall in mm, rain days tells you how often you might need an umbrella, which is useful for planning outdoor activities.

Humidity

Relative humidity as a percentage. Below 40%: Dry -- skin and throat may feel parched. 40-60%: Comfortable -- ideal for most people. 60-80%: Sticky -- light, breathable fabrics recommended. Above 80%: Muggy -- heat feels more intense; quick-dry clothing is essential.

Frequently Asked Questions: San Jose in September

In September, San Jose experiences average highs of 30°C (86°F) and lows of 23°C (73°F). Expect around 12 rainy days and 4 hours of sunshine per day, with humidity averaging 82%. The 7°C gap between daytime and overnight temperatures is worth planning around: light layers work for most visitors during the day, but an overshirt or cardigan handles the cooler evenings. UV index averages 6, so sun protection is advisable on clear days.

San Jose typically sees 12 rainy days in September, with total precipitation of around 140mm. Rain is moderate and manageable. Showers tend to pass quickly, and a light rain layer or foldable umbrella is sufficient protection for most days. For context, the driest month in San Jose typically sees 4-6 fewer rain days than September.

Pack lightweight, breathable clothing (linen or cotton), a wide-brim sun hat, SPF 50+ sunscreen, and a refillable water bottle for San Jose in September. The 30°C daytime heat demands sun protection during midday hours, typically 11am to 4pm. A compact travel umbrella is also worth packing, as 12 rainy days means afternoon showers are a real possibility. Quick-dry synthetic fabrics are preferable to cotton in 82% humidity.

September can be a challenging time to visit San Jose due to cold temperatures that rarely climb above 30°C. Indoor attractions, cultural sites, and covered markets are the strongest options this month. If your dates are flexible, the drier or milder months offer significantly easier travel conditions.

The average high temperature in San Jose in September is 30°C (86°F), and the average low is 23°C (73°F). The mean daily temperature is approximately 27°C (80°F). The day-to-night range of 7°C is moderate, meaning a single light jacket covers most situations. These are 30-year climate normals based on the 1991 to 2020 reference period; individual years will vary, particularly in transitional months like spring and autumn.

The best month to visit San Jose is generally February. February offers the most sunshine at 3 hours per day and only 9 rainy days. Average temperatures reach 29°C, making it comfortable for sightseeing, outdoor dining, and exploring the city. If your travel dates are flexible, planning your trip around February gives you the best chance of dry, bright weather.

September is shoulder or low season in San Jose, meaning fewer tourists and generally lower prices than peak months. With 4 sunshine hours and 12 rainy days, the weather is less of a draw for mass tourism. This is an advantage for travellers who prefer a quieter, more relaxed experience with shorter queues and easier accommodation availability.

In September, San Jose suits a range of activities thanks to warm temperatures of 30°C. Mix of indoor and outdoor activities works well given the moderate chance of rain. Top options include exploring historic neighbourhoods, visiting museums and galleries, local food markets, and day trips to surrounding areas. Cosy cafes and cultural venues make ideal retreats on overcast days.

September ranks 7th sunniest of the year in San Jose, with an average 4 daily sunshine hours. The driest months are December, January, and November. May is the hottest month (32°C avg high); January is the coolest (28°C). From here, temperatures fall 1°C into October. Compared to last month (August: 31°C high, 15 rain days), September is cooler and drier. September sits in the middle of the annual sunshine ranking for San Jose, offering a reasonable balance of good weather and manageable crowds.

Year-Round Climate

Month	High	Low	Rain Days	Sun	Details
January	28°C	21°C	7	1h	View
February	29°C	22°C	9	3h	View
March	30°C	23°C	12	4h	View
April	31°C	24°C	15	6h	View
May	32°C	25°C	17	7h	View
June	32°C	25°C	18	7h	View
July	32°C	25°C	17	7h	View
August	31°C	24°C	15	6h	View
September	30°C	23°C	12	4h	View
October	29°C	22°C	9	3h	View
November	28°C	21°C	7	1h	View
December	28°C	21°C	6	1h	View

Other Months in San Jose

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Plan Your Trip to San Jose

Best Time to Visit San Jose

Data Sources for San Jose

San Jose on Wikipedia Open-Meteo Climate API NOAA National Centers UK Met Office WMO GeoNames

Climate normals represent 30-year averages (1991-2020). Individual years may vary.