San José weather in September

In September, San José sees average daytime highs of 27°C and overnight lows near 23°C, with 260 mm of rain across 29.3 wet days and about 12.1 hours of daylight. It is the 5th-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 27°C through the month. The sky is clear or mostly clear about 4% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 h 12 min at the start of September to 11 h 54 min by month's end. Set against the rest of the year, September is San José's 9th-clearest and 12th-windiest month. For the whole year in context, see San José's year-round climate.

Daytime high: 27°; 5th warmest
Overnight low: 23°; 10th coldest
Rainfall: 260 mm; 29.3 wet days
Daylight: 12 h 06 min; 5:33 AM – 5:37 PM
Cloud cover: 83%; 9th clearest
Wind: 10 km/h; 12th windiest
Solar energy: 4.72 kWh/m²
Travel score: 3.4; out of 10

San José is populated place in Upala district of Costa Rico.

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

← August San José year-round climate October →Best places to visit in September

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 27°C through the month.

A typical September day in San José reaches about 27°C in the afternoon and slips back to 23°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 28°C. Set against its neighbours, September runs on par with August and on par with October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°C)	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27	27
Avg low (°C)	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23	23

	Avg high (°C)	Avg low (°C)
1	27	23
2	27	23
3	27	23
4	27	23
5	27	23
6	27	23
7	27	23
8	27	23
9	27	23
10	27	23
11	27	23
12	27	23
13	27	23
14	27	23
15	27	23
16	27	23
17	27	23
18	27	23
19	27	23
20	27	23
21	27	23
22	27	23
23	27	23
24	27	23
25	27	23
26	27	23
27	27	23
28	27	23
29	27	23
30	27	23

San José weather by month

How September compares with the rest of the year at a glance. September is the 5th-warmest and 5th-wettest month here — the current month is highlighted below.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Daylight (hours)	Travel score
Jan	26° / 22°	171	26.8	11.4	4.5
Feb	27° / 22°	113	22.1	11.6	4.8
Mar	28° / 23°	80	19.8	11.9	5.3
Apr	28° / 23°	63	18.1	12.2	4.8
May	28° / 24°	223	26.7	12.5	3.7
Jun	27° / 24°	281	29.4	12.6	3.3
Jul	27° / 23°	308	30.6	12.6	3.4
Aug	27° / 23°	259	30.5	12.4	3.4
Sep	27° / 23°	260	29.3	12.1	3.4
Oct	27° / 23°	299	29.3	11.8	3.5
Nov	26° / 23°	262	26.2	11.5	4.0
Dec	26° / 22°	214	27.3	11.4	4.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 4% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 9% of September, with mostly cloudy or overcast conditions the remaining 87%.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	15	15	15	15	15	15	15	15	15	15	13	13	13	12	12	12	12	11	11	11	12	12	12	12	12	11	11	11	12	12
Cloudier (%)	85	85	85	85	85	85	85	85	85	85	87	87	87	88	88	88	88	89	89	89	88	88	88	88	88	89	89	89	88	88

	Clearer (%)	Cloudier (%)
1	15	85
2	15	85
3	15	85
4	15	85
5	15	85
6	15	85
7	15	85
8	15	85
9	15	85
10	15	85
11	13	87
12	13	87
13	13	87
14	12	88
15	12	88
16	12	88
17	12	88
18	11	89
19	11	89
20	11	89
21	12	88
22	12	88
23	12	88
24	12	88
25	12	88
26	11	89
27	11	89
28	11	89
29	12	88
30	12	88

Chance of precipitation in September

Any precipitation

San José gets around 260 mm of rain over 29.3 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 97% and peaks near 98% on the wettest days.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	97	97	97	97	97	97	97	97	97	97	97	97	97	97	97	98	98	98	98	98	98	98	98	98	98	98	97	97	97	96

	Rain chance (%)
1	97
2	97
3	97
4	97
5	97
6	97
7	97
8	97
9	97
10	97
11	97
12	97
13	97
14	97
15	97
16	98
17	98
18	98
19	98
20	98
21	98
22	98
23	98
24	98
25	98
26	98
27	97
28	97
29	97
30	96

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels oppressive — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the oppressive band about 100% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Muggy (%)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	1	1	1	1	1
Oppressive (%)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	99	99	99	99	99	99

	Muggy (%)	Oppressive (%)
1	0	100
2	0	100
3	0	100
4	0	100
5	0	100
6	0	100
7	0	100
8	0	100
9	0	100
10	0	100
11	0	100
12	0	100
13	0	100
14	0	100
15	0	100
16	0	100
17	0	100
18	0	100
19	0	100
20	0	100
21	0	100
22	0	100
23	0	100
24	0	100
25	1	99
26	1	99
27	1	99
28	1	99
29	1	99
30	1	99

Wind in September

Winds average 10 km/h in September, the calmest month.

Across September, daily wind ranges from about 9 km/h on the calmest days to 11 km/h at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (km/h)	11	11	11	11	11	10	10	10	10	10	10	10	10	10	10	10	10	10	10	10	9	9	9	9	9	10	10	10	10	10
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

	Wind speed (km/h)	Feels
1	11	calm
2	11	calm
3	11	calm
4	11	calm
5	11	calm
6	10	calm
7	10	calm
8	10	calm
9	10	calm
10	10	calm
11	10	calm
12	10	calm
13	10	calm
14	10	calm
15	10	calm
16	10	calm
17	10	calm
18	10	calm
19	10	calm
20	10	calm
21	9	calm
22	9	calm
23	9	calm
24	9	calm
25	9	calm
26	10	calm
27	10	calm
28	10	calm
29	10	calm
30	10	calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 12 min at the start of September to 11 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 18 minutes over September. Sunrise moves from 5:34 AM to 5:32 AM, and sunset from 5:47 PM to 5:27 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	12.2	12.2	12.2	12.2	12.2	12.2	12.2	12.1	12.1	12.1	12.1	12.1	12.1	12.1	12.1	12.1	12.0	12.0	12.0	12.0	12.0	12.0	12.0	12.0	12.0	12.0	11.9	11.9	11.9	11.9
Sunrise (AM)	5:34	5:34	5:34	5:34	5:34	5:34	5:34	5:34	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:33	5:32	5:32	5:32
Sunset (PM)	5:47	5:46	5:45	5:45	5:44	5:43	5:43	5:42	5:41	5:41	5:40	5:39	5:39	5:38	5:37	5:37	5:36	5:35	5:35	5:34	5:33	5:33	5:32	5:31	5:31	5:30	5:29	5:29	5:28	5:27

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	12.2	5:34	5:47
2	12.2	5:34	5:46
3	12.2	5:34	5:45
4	12.2	5:34	5:45
5	12.2	5:34	5:44
6	12.2	5:34	5:43
7	12.2	5:34	5:43
8	12.1	5:34	5:42
9	12.1	5:33	5:41
10	12.1	5:33	5:41
11	12.1	5:33	5:40
12	12.1	5:33	5:39
13	12.1	5:33	5:39
14	12.1	5:33	5:38
15	12.1	5:33	5:37
16	12.1	5:33	5:37
17	12.0	5:33	5:36
18	12.0	5:33	5:35
19	12.0	5:33	5:35
20	12.0	5:33	5:34
21	12.0	5:33	5:33
22	12.0	5:33	5:33
23	12.0	5:33	5:32
24	12.0	5:33	5:31
25	12.0	5:33	5:31
26	12.0	5:33	5:30
27	11.9	5:33	5:29
28	11.9	5:32	5:29
29	11.9	5:32	5:28
30	11.9	5:32	5:27

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.72 kWh/m².

For context, solar energy here swings from a low near 3.98 kWh/m² to a high of 6.04 kWh/m² in April across the year — September's 4.72 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.8	4.7	4.7	4.7	4.7	4.7	4.7	4.7	4.7	4.7	4.6	4.6	4.6	4.6	4.6	4.6	4.5	4.5	4.5
Level	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright

	Solar energy (kWh/m²)	Level
1	4.8	Bright
2	4.8	Bright
3	4.8	Bright
4	4.8	Bright
5	4.8	Bright
6	4.8	Bright
7	4.8	Bright
8	4.8	Bright
9	4.8	Bright
10	4.8	Bright
11	4.8	Bright
12	4.8	Bright
13	4.7	Bright
14	4.7	Bright
15	4.7	Bright
16	4.7	Bright
17	4.7	Bright
18	4.7	Bright
19	4.7	Bright
20	4.7	Bright
21	4.7	Bright
22	4.6	Bright
23	4.6	Bright
24	4.6	Bright
25	4.6	Bright
26	4.6	Bright
27	4.6	Bright
28	4.5	Bright
29	4.5	Bright
30	4.5	Bright

Planning a trip in September

Is September a good time to visit San José?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

3.4

Sightseeing

9th-best month of the year

3.5

Beach & pool

9th-best month of the year

September is a weaker month for outdoor sightseeing in San José.

What to pack for San José in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, San José sees daytime highs around 27°C and nights near 23°C. Pack light clothes and rain gear. Worth having: sun protection. About 29 days see rain.

light clothesrain gearsun protection

Sea temperature near San José in September

The nearest coast averages about 29°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 65 km away) is warmest in May at about 29°C and coldest in February near 27°C.

The water stays above 20°C all year — warm enough for a swim any month.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sea temperature (°C)	27	27	27	29	29	29	29	29	29	28	28	27
Comfort	Warm	Warm	Warm	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Warm	Warm

	Sea temperature (°C)	Comfort
Jan	27	Warm
Feb	27	Warm
Mar	27	Warm
Apr	29	Tropical
May	29	Tropical
Jun	29	Tropical
Jul	29	Tropical
Aug	29	Tropical
Sep	29	Tropical
Oct	28	Tropical
Nov	28	Warm
Dec	27	Warm

UV index in San José in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 12 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San José peaks around March 18 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 9 (very high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	11	13	14	14	13	13	12	13	12	12	11	9
Level	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Extreme	Very high

	UV index (midday)	Level
Jan	11	Extreme
Feb	13	Extreme
Mar	14	Extreme
Apr	14	Extreme
May	13	Extreme
Jun	13	Extreme
Jul	12	Extreme
Aug	13	Extreme
Sep	12	Extreme
Oct	12	Extreme
Nov	11	Extreme
Dec	9	Very high

Air quality in San José in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in San José is worst in July — around 23 µg/m³ PM2.5 (moderate), about 3.8× the cleanest month (December, 6 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
PM2.5 (µg/m³)	7	8	9	19	21	19	23	18	13	9	6	6
Level	Good	Good	Good	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Good	Good	Good

	PM2.5 (µg/m³)	Level
Jan	7	Good
Feb	8	Good
Mar	9	Good
Apr	19	Moderate
May	21	Moderate
Jun	19	Moderate
Jul	23	Moderate
Aug	18	Moderate
Sep	13	Moderate
Oct	9	Good
Nov	6	Good
Dec	6	Good

Location & terrain

Where is San José?

San José sits at 11.0°N, 85.1°W, 50 m above sea level, in Costa Rica. The nearest listed city is San Carlos, 44 km away.

Topography around San José

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of San José.

Within 3 km, the terrain around San José has only modest variations in elevation — a maximum elevation change of 55 m around an average of 51 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 659 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,977 m.

The land around San José is covered by grassland (51%) and trees (48%) within 3 km, trees (59%) and grassland (36%) within 16 km, and trees (45%), water (27%) and grassland (24%) within 80 km.

3 km

55 m

grassland 51%

16 km

659 m

trees 59%

80 km

1,977 m

trees 45%

treesgrasslandcroplandartificial surfaceswater

← August San José year-round climate October →Best places to visit in September

September weather nearby: San Carlos 44 km · Liberia 48 km · Cañas 58 km · La Fortuna 76 km · Monteverde 80 km · El Castillo 81 km · San Juan del Sur 87 km · Rivas 93 km

Costa Rica travel facts

Travel advisory: Level 2; Exercise Increased Caution
Power plugs: Type A / B; 120 V · 60 Hz
Prices: ≈ 59% of US; price level, 2025
GDP per capita: $19,970; 2025
Happiness: 7.4 / 10; World Happiness, 2025
Safe drinking water: 81%; of population, 2024
Homicide rate: 17.7; per 100k, 2023
Road deaths: 14.8; per 100k/yr, 2019
Income group: High; World Bank
English: Moderate; EF EPI 516
Religion

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for San José (10.9519°, -85.1357°, elevation 50 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).

	Avg high (°C)	Avg low (°C)
1	27	23
2	27	23
3	27	23
4	27	23
5	27	23
6	27	23
7	27	23
8	27	23
9	27	23
10	27	23
11	27	23
12	27	23
13	27	23
14	27	23
15	27	23
16	27	23
17	27	23
18	27	23
19	27	23
20	27	23
21	27	23
22	27	23
23	27	23
24	27	23
25	27	23
26	27	23
27	27	23
28	27	23
29	27	23
30	27	23

	Clearer (%)	Cloudier (%)
1	15	85
2	15	85
3	15	85
4	15	85
5	15	85
6	15	85
7	15	85
8	15	85
9	15	85
10	15	85
11	13	87
12	13	87
13	13	87
14	12	88
15	12	88
16	12	88
17	12	88
18	11	89
19	11	89
20	11	89
21	12	88
22	12	88
23	12	88
24	12	88
25	12	88
26	11	89
27	11	89
28	11	89
29	12	88
30	12	88

	Rain chance (%)
1	97
2	97
3	97
4	97
5	97
6	97
7	97
8	97
9	97
10	97
11	97
12	97
13	97
14	97
15	97
16	98
17	98
18	98
19	98
20	98
21	98
22	98
23	98
24	98
25	98
26	98
27	97
28	97
29	97
30	96

	Muggy (%)	Oppressive (%)
1	0	100
2	0	100
3	0	100
4	0	100
5	0	100
6	0	100
7	0	100
8	0	100
9	0	100
10	0	100
11	0	100
12	0	100
13	0	100
14	0	100
15	0	100
16	0	100
17	0	100
18	0	100
19	0	100
20	0	100
21	0	100
22	0	100
23	0	100
24	0	100
25	1	99
26	1	99
27	1	99
28	1	99
29	1	99
30	1	99

	Avg high (°C)	Avg low (°C)
1	27	23
2	27	23
3	27	23
4	27	23
5	27	23
6	27	23
7	27	23
8	27	23
9	27	23
10	27	23
11	27	23
12	27	23
13	27	23
14	27	23
15	27	23
16	27	23
17	27	23
18	27	23
19	27	23
20	27	23
21	27	23
22	27	23
23	27	23
24	27	23
25	27	23
26	27	23
27	27	23
28	27	23
29	27	23
30	27	23

	Clearer (%)	Cloudier (%)
1	15	85
2	15	85
3	15	85
4	15	85
5	15	85
6	15	85
7	15	85
8	15	85
9	15	85
10	15	85
11	13	87
12	13	87
13	13	87
14	12	88
15	12	88
16	12	88
17	12	88
18	11	89
19	11	89
20	11	89
21	12	88
22	12	88
23	12	88
24	12	88
25	12	88
26	11	89
27	11	89
28	11	89
29	12	88
30	12	88

	Rain chance (%)
1	97
2	97
3	97
4	97
5	97
6	97
7	97
8	97
9	97
10	97
11	97
12	97
13	97
14	97
15	97
16	98
17	98
18	98
19	98
20	98
21	98
22	98
23	98
24	98
25	98
26	98
27	97
28	97
29	97
30	96

	Muggy (%)	Oppressive (%)
1	0	100
2	0	100
3	0	100
4	0	100
5	0	100
6	0	100
7	0	100
8	0	100
9	0	100
10	0	100
11	0	100
12	0	100
13	0	100
14	0	100
15	0	100
16	0	100
17	0	100
18	0	100
19	0	100
20	0	100
21	0	100
22	0	100
23	0	100
24	0	100
25	1	99
26	1	99
27	1	99
28	1	99
29	1	99
30	1	99

	Avg high (°C)	Avg low (°C)
1	27	23
2	27	23
3	27	23
4	27	23
5	27	23
6	27	23
7	27	23
8	27	23
9	27	23
10	27	23
11	27	23
12	27	23
13	27	23
14	27	23
15	27	23
16	27	23
17	27	23
18	27	23
19	27	23
20	27	23
21	27	23
22	27	23
23	27	23
24	27	23
25	27	23
26	27	23
27	27	23
28	27	23
29	27	23
30	27	23

	Clearer (%)	Cloudier (%)
1	15	85
2	15	85
3	15	85
4	15	85
5	15	85
6	15	85
7	15	85
8	15	85
9	15	85
10	15	85
11	13	87
12	13	87
13	13	87
14	12	88
15	12	88
16	12	88
17	12	88
18	11	89
19	11	89
20	11	89
21	12	88
22	12	88
23	12	88
24	12	88
25	12	88
26	11	89
27	11	89
28	11	89
29	12	88
30	12	88

	Rain chance (%)
1	97
2	97
3	97
4	97
5	97
6	97
7	97
8	97
9	97
10	97
11	97
12	97
13	97
14	97
15	97
16	98
17	98
18	98
19	98
20	98
21	98
22	98
23	98
24	98
25	98
26	98
27	97
28	97
29	97
30	96

	Muggy (%)	Oppressive (%)
1	0	100
2	0	100
3	0	100
4	0	100
5	0	100
6	0	100
7	0	100
8	0	100
9	0	100
10	0	100
11	0	100
12	0	100
13	0	100
14	0	100
15	0	100
16	0	100
17	0	100
18	0	100
19	0	100
20	0	100
21	0	100
22	0	100
23	0	100
24	0	100
25	1	99
26	1	99
27	1	99
28	1	99
29	1	99
30	1	99