Jaco weather in September

In September, Jaco sees average daytime highs of 27°C and overnight lows near 25°C, with 470 mm of rain across 29.1 wet days and about 12.1 hours of daylight. It is the 10th-warmest and 3rd-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 1% 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 Jaco's 9th-clearest and 2nd-windiest month. For the whole year in context, see Jaco's year-round climate.

Daytime high: 27°; 10th warmest
Overnight low: 25°; 3rd coldest
Rainfall: 470 mm; 29.1 wet days
Daylight: 12 h 06 min; 5:31 AM – 5:34 PM
Cloud cover: 89%; 9th clearest
Wind: 11 km/h; 2nd windiest
Solar energy: 4.53 kWh/m²
Travel score: 3.4; out of 10

← August Jaco 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 Jaco reaches about 27°C in the afternoon and slips back to 25°C overnight — a 2°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)	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25	25

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

Jaco weather by month

How September compares with the rest of the year at a glance. September is the 10th-warmest and 3rd-wettest month here — the current month is highlighted below.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Daylight (hours)	Travel score
Jan	27° / 26°	28	6.3	11.5	7.4
Feb	28° / 27°	16	3.4	11.7	7.9
Mar	28° / 27°	23	5.8	11.9	7.3
Apr	28° / 26°	108	18.4	12.2	5.1
May	28° / 26°	405	28.3	12.4	3.6
Jun	27° / 26°	430	28.4	12.6	3.4
Jul	27° / 26°	456	29	12.5	3.4
Aug	27° / 26°	506	29.4	12.3	3.4
Sep	27° / 25°	470	29.1	12.1	3.4
Oct	27° / 25°	571	29.3	11.8	3.5
Nov	27° / 25°	371	25.6	11.6	4.1
Dec	27° / 26°	123	15.2	11.4	5.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 1% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 3% of September, with mostly cloudy or overcast conditions the remaining 96%.

	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 (%)	4	4	4	4	4	4	3	3	3	3	3	3	2	2	4	4	4	4	4	4	5	5	5	5	5	5	5	5	5	5
Cloudier (%)	96	96	96	96	96	96	97	97	97	97	97	97	98	98	96	96	96	96	96	96	95	95	95	95	95	95	95	95	95	95

	Clearer (%)	Cloudier (%)
1	4	96
2	4	96
3	4	96
4	4	96
5	4	96
6	4	96
7	3	97
8	3	97
9	3	97
10	3	97
11	3	97
12	3	97
13	2	98
14	2	98
15	4	96
16	4	96
17	4	96
18	4	96
19	4	96
20	4	96
21	5	95
22	5	95
23	5	95
24	5	95
25	5	95
26	5	95
27	5	95
28	5	95
29	5	95
30	5	95

Chance of precipitation in September

Any precipitation

Jaco gets around 470 mm of rain over 29.1 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 97% 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	97	97	97	97	97	97	97	97	96	96	96	96	96	95	95

	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	97
17	97
18	97
19	97
20	97
21	97
22	97
23	97
24	96
25	96
26	96
27	96
28	96
29	95
30	95

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 94% 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
Oppressive (%)	93	93	93	93	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	94	95	95	95	95	95	95
Miserable (%)	7	7	7	7	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	5	5	5	5	5	5

	Oppressive (%)	Miserable (%)
1	93	7
2	93	7
3	93	7
4	93	7
5	94	6
6	94	6
7	94	6
8	94	6
9	94	6
10	94	6
11	94	6
12	94	6
13	94	6
14	94	6
15	94	6
16	94	6
17	94	6
18	94	6
19	94	6
20	94	6
21	94	6
22	94	6
23	94	6
24	94	6
25	95	5
26	95	5
27	95	5
28	95	5
29	95	5
30	95	5

Wind in September

Winds average 11 km/h in September.

Across September, daily wind ranges from about 10 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)	10	10	10	10	10	10	10	10	10	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11
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	10	calm
2	10	calm
3	10	calm
4	10	calm
5	10	calm
6	10	calm
7	10	calm
8	10	calm
9	10	calm
10	11	calm
11	11	calm
12	11	calm
13	11	calm
14	11	calm
15	11	calm
16	11	calm
17	11	calm
18	11	calm
19	11	calm
20	11	calm
21	11	calm
22	11	calm
23	11	calm
24	11	calm
25	11	calm
26	11	calm
27	11	calm
28	11	calm
29	11	calm
30	11	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 5:33 AM to 5:30 AM, and sunset from 5:44 PM to 5:26 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	12.1	12.1	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	12.0	11.9	11.9	11.9
Sunrise (AM)	5:33	5:33	5:32	5:32	5:32	5:32	5:32	5:32	5:32	5:32	5:32	5:32	5:32	5:31	5:31	5:31	5:31	5:31	5:31	5:31	5:31	5:31	5:31	5:31	5:30	5:30	5:30	5:30	5:30	5:30
Sunset (PM)	5:44	5:43	5:43	5:42	5:41	5:41	5:40	5:40	5:39	5:38	5:38	5:37	5:36	5:36	5:35	5:34	5:34	5:33	5:32	5:32	5:31	5:31	5:30	5:29	5:29	5:28	5:27	5:27	5:26	5:26

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

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.53 kWh/m².

For context, solar energy here swings from a low near 4.12 kWh/m² to a high of 6.51 kWh/m² in March across the year — September's 4.53 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)	4.6	4.6	4.6	4.6	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.4	4.4
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	4.6	Bright
2	4.6	Bright
3	4.6	Bright
4	4.6	Bright
5	4.5	Bright
6	4.5	Bright
7	4.5	Bright
8	4.5	Bright
9	4.5	Bright
10	4.5	Bright
11	4.5	Bright
12	4.5	Bright
13	4.5	Bright
14	4.5	Bright
15	4.5	Bright
16	4.5	Bright
17	4.5	Bright
18	4.5	Bright
19	4.5	Bright
20	4.5	Bright
21	4.5	Bright
22	4.5	Bright
23	4.5	Bright
24	4.5	Bright
25	4.5	Bright
26	4.5	Bright
27	4.5	Bright
28	4.5	Bright
29	4.4	Bright
30	4.4	Bright

Planning a trip in September

Hazard calendar for Jaco

In seasonPeak

In September, Jaco sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

Jaco's rainy season runs May–November, when most of the year's rain falls.

Rainy season

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Is September a good time to visit Jaco?

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

12th-best month of the year

September is a weaker month for outdoor sightseeing in Jaco.

What to pack for Jaco in September

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

In September, Jaco sees daytime highs around 27°C and nights near 25°C. Pack rain gear. Worth having: light clothes and sun protection. About 29 days see rain.

rain gearlight clothessun protection

Sea temperature near Jaco 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 offshore is warmest in April at about 29°C and coldest in November near 28°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)	29	29	29	29	29	29	29	29	29	28	28	28
Comfort	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Tropical	Warm	Tropical

	Sea temperature (°C)	Comfort
Jan	29	Tropical
Feb	29	Tropical
Mar	29	Tropical
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	28	Tropical

UV index in Jaco 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 Jaco peaks around March 15 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 17 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	13	13	12	13	11	12	12	11	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	13	Extreme
Apr	13	Extreme
May	12	Extreme
Jun	13	Extreme
Jul	11	Extreme
Aug	12	Extreme
Sep	12	Extreme
Oct	11	Extreme
Nov	11	Extreme
Dec	9	Very high

Air quality in Jaco 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 Jaco is worst in May — around 18 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (January, 9 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)	9	10	11	16	18	16	17	15	14	12	11	9
Level	Good	Good	Good	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Good	Good

	PM2.5 (µg/m³)	Level
Jan	9	Good
Feb	10	Good
Mar	11	Good
Apr	16	Moderate
May	18	Moderate
Jun	16	Moderate
Jul	17	Moderate
Aug	15	Moderate
Sep	14	Moderate
Oct	12	Moderate
Nov	11	Good
Dec	9	Good

Location & terrain

Where is Jaco?

Jaco sits at 9.6°N, 84.6°W, 0 m above sea level, in Costa Rica. The nearest listed city is Esparza, 42 km away.

Topography around Jaco

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

Within 3 km, the terrain around Jaco has significant variations in elevation — a maximum elevation change of 401 m around an average of 35 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 802 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,811 m.

The land around Jaco is covered by water (38%) and trees (31%) within 3 km, water (56%) and trees (35%) within 16 km, and trees (45%) and water (43%) within 80 km.

3 km

401 m

water 38%

16 km

802 m

water 56%

80 km

2,811 m

trees 45%

treesgrasslandcroplandartificial surfacesbare terrainwatermangroves

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

September weather nearby: Esparza 42 km · Chacarita 44 km · San Rafael Abajo 44 km · Tejar 46 km · Puntarenas 46 km · San_Ramon_ 55 km · Manuel Antonio 57 km · Alajuela 64 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 Jaco (9.615°, -84.6298°, elevation 0 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	25
2	27	25
3	27	25
4	27	25
5	27	25
6	27	25
7	27	25
8	27	25
9	27	25
10	27	25
11	27	25
12	27	25
13	27	25
14	27	25
15	27	25
16	27	25
17	27	25
18	27	25
19	27	25
20	27	25
21	27	25
22	27	25
23	27	25
24	27	25
25	27	25
26	27	25
27	27	25
28	27	25
29	27	25
30	27	25

	Clearer (%)	Cloudier (%)
1	4	96
2	4	96
3	4	96
4	4	96
5	4	96
6	4	96
7	3	97
8	3	97
9	3	97
10	3	97
11	3	97
12	3	97
13	2	98
14	2	98
15	4	96
16	4	96
17	4	96
18	4	96
19	4	96
20	4	96
21	5	95
22	5	95
23	5	95
24	5	95
25	5	95
26	5	95
27	5	95
28	5	95
29	5	95
30	5	95

	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	97
17	97
18	97
19	97
20	97
21	97
22	97
23	97
24	96
25	96
26	96
27	96
28	96
29	95
30	95

	Oppressive (%)	Miserable (%)
1	93	7
2	93	7
3	93	7
4	93	7
5	94	6
6	94	6
7	94	6
8	94	6
9	94	6
10	94	6
11	94	6
12	94	6
13	94	6
14	94	6
15	94	6
16	94	6
17	94	6
18	94	6
19	94	6
20	94	6
21	94	6
22	94	6
23	94	6
24	94	6
25	95	5
26	95	5
27	95	5
28	95	5
29	95	5
30	95	5

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

	Clearer (%)	Cloudier (%)
1	4	96
2	4	96
3	4	96
4	4	96
5	4	96
6	4	96
7	3	97
8	3	97
9	3	97
10	3	97
11	3	97
12	3	97
13	2	98
14	2	98
15	4	96
16	4	96
17	4	96
18	4	96
19	4	96
20	4	96
21	5	95
22	5	95
23	5	95
24	5	95
25	5	95
26	5	95
27	5	95
28	5	95
29	5	95
30	5	95

	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	97
17	97
18	97
19	97
20	97
21	97
22	97
23	97
24	96
25	96
26	96
27	96
28	96
29	95
30	95

	Oppressive (%)	Miserable (%)
1	93	7
2	93	7
3	93	7
4	93	7
5	94	6
6	94	6
7	94	6
8	94	6
9	94	6
10	94	6
11	94	6
12	94	6
13	94	6
14	94	6
15	94	6
16	94	6
17	94	6
18	94	6
19	94	6
20	94	6
21	94	6
22	94	6
23	94	6
24	94	6
25	95	5
26	95	5
27	95	5
28	95	5
29	95	5
30	95	5

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

	Clearer (%)	Cloudier (%)
1	4	96
2	4	96
3	4	96
4	4	96
5	4	96
6	4	96
7	3	97
8	3	97
9	3	97
10	3	97
11	3	97
12	3	97
13	2	98
14	2	98
15	4	96
16	4	96
17	4	96
18	4	96
19	4	96
20	4	96
21	5	95
22	5	95
23	5	95
24	5	95
25	5	95
26	5	95
27	5	95
28	5	95
29	5	95
30	5	95

	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	97
17	97
18	97
19	97
20	97
21	97
22	97
23	97
24	96
25	96
26	96
27	96
28	96
29	95
30	95

	Oppressive (%)	Miserable (%)
1	93	7
2	93	7
3	93	7
4	93	7
5	94	6
6	94	6
7	94	6
8	94	6
9	94	6
10	94	6
11	94	6
12	94	6
13	94	6
14	94	6
15	94	6
16	94	6
17	94	6
18	94	6
19	94	6
20	94	6
21	94	6
22	94	6
23	94	6
24	94	6
25	95	5
26	95	5
27	95	5
28	95	5
29	95	5
30	95	5