Costa Rica weather in September

In September, Costa Rica sees average daytime highs of 33°C and overnight lows near 26°C, with 175 mm of rain across 18.4 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 1st-wettest month of the year here.

Day-to-day highs hold fairly steady near 33°C through the month. The sky is clear or mostly clear about 27% of the time in September, and the air most often feels miserable.

Daylight stretches from about 12 h 30 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Costa Rica's 10th-clearest and 11th-windiest month. For the whole year in context, see Costa Rica's year-round climate.

Daytime high
33°
4th warmest
Overnight low
26°
10th coldest
Rainfall
175 mm
18.4 wet days
Daylight
12 h 06 min
6:00 AM – 6:08 PM
Cloud cover
62%
10th clearest
Wind
7 km/h
11th windiest
Solar energy
5.04 kWh/m²
Travel score
2.9
out of 10

Costa Rica is town in Culiacán Municipality, State of Sinaloa, Mexico.

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 33°C through the month.

A typical September day in Costa Rica reaches about 33°C in the afternoon and slips back to 26°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 31°C and 35°C. Set against its neighbours, September runs on par with August and on par with October.

20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13326
23326
33326
43326
53326
63326
73326
83326
93326
103326
113326
123326
133326
143326
153326
163326
173326
183326
193326
203326
213326
223326
233326
243326
253326
263326
273326
283326
293326
303326

How September really feels in Costa Rica

Once humidity and wind are folded in, September averages 30 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
30
30 feel dangerously hot (≥ 39°C)
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Costa Rica weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan26° / 14°131.710.68.4
Feb26° / 15°141.611.18.3
Mar27° / 16°30.511.88.2
Apr29° / 18°10.212.66.9
May31° / 21°10.213.25.7
Jun33° / 25°14213.54.5
Jul34° / 26°10813.713.42.9
Aug33° / 26°16819.112.92.6
Sep33° / 26°17518.412.22.9
Oct32° / 24°434.711.44.6
Nov30° / 19°382.210.86.6
Dec26° / 15°141.710.58.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 27% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 20% of September, with mostly cloudy or overcast conditions the remaining 53%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
12872
22971
33070
43070
53268
63367
73466
83664
93763
103862
114060
124159
134258
144456
154555
164654
174753
184951
195050
205248
215446
225644
235743
245941
256139
266337
276535
286733
296931
307129

Chance of precipitation in September

Any precipitation

Costa Rica gets around 175 mm of rain over 18.4 wet days in September, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 60% and peaks near 72% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%151015202530
Rain chance (%)
172
272
372
472
571
671
770
870
969
1068
1167
1266
1365
1464
1563
1662
1761
1860
1958
2057
2155
2253
2351
2449
2547
2645
2743
2841
2939
3037

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the miserable band about 97% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Oppressive (%)Miserable (%)
1199
2199
3199
4199
5199
6199
7199
8199
9199
10298
11298
12298
13298
14298
15298
16298
17298
18298
19397
20397
21397
22496
23496
24496
25595
26694
27694
28793
29892
30991

Wind in September

Winds average 7 km/h in September.

Across September, daily wind ranges from about 6 km/h on the calmest days to 7 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
276calm
286calm
296calm
306calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 30 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 42 minutes over September. Sunrise moves from 5:54 AM to 6:05 AM, and sunset from 6:24 PM to 5:53 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.55:546:24
212.55:556:23
312.55:556:22
412.45:556:21
512.45:566:20
612.45:566:19
712.45:566:18
812.35:576:17
912.35:576:16
1012.35:576:15
1112.35:586:14
1212.25:586:13
1312.25:596:11
1412.25:596:10
1512.25:596:09
1612.16:006:08
1712.16:006:07
1812.16:006:06
1912.16:016:05
2012.06:016:04
2112.06:016:03
2212.06:026:01
2312.06:026:00
2411.96:035:59
2511.96:035:58
2611.96:035:57
2711.96:045:56
2811.86:045:55
2911.86:055:54
3011.86:055:53

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.04 kWh/m².

For context, solar energy here swings from a low near 4.14 kWh/m² to a high of 7.81 kWh/m² in May across the year — September's 5.04 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.0Bright
45.0Bright
55.0Bright
65.0Bright
75.0Bright
85.0Bright
95.0Bright
105.0Bright
115.0Bright
125.0Bright
135.0Bright
145.0Bright
155.0Bright
165.0Bright
175.0Bright
185.1Bright
195.1Bright
205.1Bright
215.1Bright
225.1Bright
235.1Bright
245.1Bright
255.2Bright
265.2Bright
275.2Bright
285.2Bright
295.2Bright
305.3Bright
Planning a trip in September

Hazard calendar for Costa Rica

In seasonPeak

In September, Costa Rica sits inside its pacific hurricane and rainy season season. The full year is below, with each hazard's peak months called out.

Costa Rica sits in the eastern Pacific hurricane zone; the season peaks August–September.

Costa Rica's rainy season runs July–September, when most of the year's rain falls.

Pacific hurricane
Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Costa Rica?

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

2.9
Sightseeing
10th-best month of the year
5.1
Beach & pool
11th-best month of the year

September is a weaker month for outdoor sightseeing in Costa Rica.

What to pack for Costa Rica in September

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

In September, Costa Rica sees daytime highs around 33°C and nights near 26°C. Pack light clothes and rain gear. Worth having: sun protection. About 18 days see rain.

light clothesrain gearsun protection

Sea temperature near Costa Rica in September

The nearest coast averages about 30°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 34 km away) is warmest in August at about 30°C and coldest in February near 21°C.

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

20°25°30°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan21Refreshing
Feb21Refreshing
Mar21Refreshing
Apr22Refreshing
May25Warm
Jun28Warm
Jul29Tropical
Aug30Tropical
Sep30Tropical
Oct29Tropical
Nov26Warm
Dec23Refreshing

UV index in Costa Rica in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Costa Rica peaks around May 11 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 5 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecHighVery highExtremeVery highHighMay 11UV 12Dec 22UV 5
UV index (midday)Level
Jan5High
Feb8Very high
Mar10Very high
Apr12Extreme
May12Extreme
Jun11Extreme
Jul12Extreme
Aug11Extreme
Sep10Extreme
Oct8Very high
Nov6High
Dec5High

Air quality in Costa Rica 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 Costa Rica is worst in May — around 43 µg/m³ PM2.5 (poor), about 3.9× the cleanest month (January, 11 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateModerateGoodMay 1740 µg/m³Jan 111 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb11Good
Mar13Moderate
Apr18Moderate
May43Poor
Jun23Moderate
Jul17Moderate
Aug12Good
Sep13Moderate
Oct13Moderate
Nov11Good
Dec11Good
Location & terrain

Where is Costa Rica?

Costa Rica sits at 24.6°N, 107.4°W, 30 m above sea level, in Mexico. The nearest listed city is Licenciado Benito Juárez, 17 km away.

Mazatlan

Topography around Costa Rica

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

Within 3 km, the terrain around Costa Rica has only modest variations in elevation — a maximum elevation change of 21 m around an average of 25 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 401 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,932 m.

The land around Costa Rica is covered by cropland (64%) within 3 km, cropland (62%) within 16 km, and trees (39%), water (27%) and cropland (20%) within 80 km.

3 km
21 m
16 km
401 m
80 km
1,932 m
treesshrubsgrasslandcroplandartificial surfacesbare terrainwatermangroves
September weather nearby: Licenciado Benito Juárez 17 km · Culiacán 24 km · Navolato 37 km · La Cruz 90 km · Guamúchil 119 km · Guasave 154 km · Gabriel Leyva Solano 173 km · Mazatlan 181 km

Mexico travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type A / B
120 / 127 V · 60 Hz
Prices
≈ 54% of US
price level, 2025
GDP per capita
$13,889
2025
Happiness
7.0 / 10
World Happiness, 2025
Safe drinking water
43%
of population, 2024
Homicide rate
24.9
per 100k, 2023
Road deaths
12.8
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Very low
EF EPI 440
Religion
Catholic 78%no religion 11%other Evangelical Churches 8%Jehovah Witness 1%

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 Costa Rica (24.5907°, -107.3899°, elevation 30 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).