Costa Rica weather in September

In September, Costa Rica sees average daytime highs of 31°C and overnight lows near 20°C, with 67 mm of rain across 8.7 wet days and about 11.9 hours of daylight. It is the 1st-warmest and 8th-wettest month of the year here.

Day-to-day highs hold fairly steady near 31°C through the month. The sky is clear or mostly clear about 51% of the time in September, and the air most often feels dry.

Daylight stretches from about 11 h 36 min at the start of September to 12 h 06 min by month's end. Set against the rest of the year, September is Costa Rica's 4th-clearest and 2nd-windiest month. For the whole year in context, see Costa Rica's year-round climate.

Daytime high
31°
1st warmest
Overnight low
20°
6th coldest
Rainfall
67 mm
8.7 wet days
Daylight
11 h 54 min
6:30 AM – 6:24 PM
Cloud cover
44%
4th clearest
Wind
9 km/h
2nd windiest
Solar energy
5.7 kWh/m²
Travel score
4.5
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 31°C through the month.

A typical September day in Costa Rica reaches about 31°C in the afternoon and slips back to 20°C overnight — a 12°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 35°C. Set against its neighbours, September runs about 1°C warmer than August and on par with October.

15°20°25°30°35°40°151015202530
Avg high (°C)Avg low (°C)
13119
23119
33119
43119
53119
63220
73220
83220
93220
103220
113220
123220
133220
143220
153220
163220
173220
183220
193220
203120
213120
223120
233120
243120
253120
263120
273120
283120
293120
303120

How September really feels in Costa Rica

Once humidity and wind are folded in, September averages 0 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
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Costa Rica weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan29° / 21°25626.2133.3
Feb29° / 21°21523.612.63.3
Mar30° / 21°18123.812.13.6
Apr29° / 20°8112.411.65.0
May28° / 18°395.711.17.0
Jun28° / 17°182.410.97.9
Jul28° / 16°111.4117.6
Aug30° / 18°172.511.46.0
Sep31° / 20°678.711.94.5
Oct31° / 21°12918.512.43.7
Nov30° / 21°17522.212.93.5
Dec29° / 21°21725.613.13.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 51% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 31%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17822
27822
37822
47822
57723
67723
77624
87525
97525
107426
117327
127327
137129
147129
157030
166931
176931
186733
196733
206535
216535
226337
236337
246139
256040
265941
275842
285743
295644
305545

Chance of precipitation in September

Any precipitation

Costa Rica gets around 67 mm of rain over 8.7 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 29% and peaks near 47% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
118
219
319
420
521
621
722
822
923
1023
1124
1224
1325
1425
1526
1627
1728
1829
1930
2031
2133
2234
2336
2437
2539
2641
2742
2844
2946
3047

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 33% of days. Sticky, muggy-or-worse air turns up on roughly 20% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
157221560
255221670
353221780
453221780
551221890
6502219100
7482220110
8472221110
9452221120
10432222130
11412223130
12392225140
13372326150
14352327160
15332328170
16312329170
17302229190
18282230200
19262231210
20252231230
21232131240
22222131260
23202031280
24192031310
25181930330
26171830350
27161729380
28151628400
29141627420
30141527441

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
510calm
610calm
710calm
810calm
910calm
1010calm
1110calm
1210calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 11 h 36 min at the start of September to 12 h 06 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 30 minutes over September. Sunrise moves from 6:43 AM to 6:17 AM, and sunset from 6:21 PM to 6:26 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.66:436:21
211.66:426:21
311.76:426:22
411.76:416:22
511.76:406:22
611.76:396:22
711.76:386:22
811.86:376:22
911.86:366:23
1011.86:356:23
1111.86:346:23
1211.86:346:23
1311.86:336:23
1411.96:326:23
1511.96:316:24
1611.96:306:24
1711.96:296:24
1811.96:286:24
1912.06:276:24
2012.06:266:24
2112.06:256:25
2212.06:246:25
2312.06:246:25
2412.06:236:25
2512.16:226:25
2612.16:216:25
2712.16:206:26
2812.16:196:26
2912.16:186:26
3012.16:176:26

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.7 kWh/m².

For context, solar energy here swings from a low near 4.17 kWh/m² to a high of 5.99 kWh/m² in October across the year — September's 5.7 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.5Bright
25.5Bright
35.5Bright
45.5Bright
55.5Bright
65.5Bright
75.6Bright
85.6Bright
95.6Bright
105.6Bright
115.6Bright
125.6Bright
135.7Bright
145.7Bright
155.7Bright
165.7Bright
175.7Bright
185.7Bright
195.7Bright
205.8Bright
215.8Bright
225.8Bright
235.8Bright
245.8Bright
255.8Bright
265.8Bright
275.9Bright
285.9Bright
295.9Bright
305.9Bright
Planning a trip in September

Hazard calendar for Costa Rica

In seasonPeak

None of Costa Rica's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Costa Rica's monsoon runs October–March, when most of the year's rain falls.

Monsoon
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).

4.5
Sightseeing
6th-best month of the year
6.9
Beach & pool
5th-best month of the year

September is a reasonable time to visit Costa Rica for sightseeing. The water and warmth also suit a beach or pool day.

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 31°C and nights near 20°C. Pack light clothes. Worth having: rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

UV index in Costa Rica in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 9 (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 January 22 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 21 at about 7 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeJan 22UV 15Jun 21UV 7
UV index (midday)Level
Jan15Extreme
Feb15Extreme
Mar14Extreme
Apr11Extreme
May8Very high
Jun7Very high
Jul8Very high
Aug9Very high
Sep9Very high
Oct10Extreme
Nov13Extreme
Dec14Extreme

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 September — around 24 µg/m³ PM2.5 (moderate), about 5.2× the cleanest month (June, 5 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 1722 µg/m³Jun 125 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb7Good
Mar6Good
Apr5Good
May5Good
Jun5Good
Jul8Good
Aug10Good
Sep24Moderate
Oct12Moderate
Nov6Good
Dec6Good
Location & terrain

Where is Costa Rica?

Costa Rica sits at 18.5°S, 53.1°W, 646 m above sea level, in Brazil. The nearest listed city is Chapadão do Sul, 60 km away.

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 160 m around an average of 655 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 307 m; within 80 km, large variations in elevation — a maximum elevation change of 616 m.

The land around Costa Rica is covered by grassland (39%) and trees (22%) within 3 km, cropland (41%), grassland (28%) and trees (27%) within 16 km, and cropland (42%), grassland (31%) and trees (23%) within 80 km.

3 km
160 m
16 km
307 m
80 km
616 m
treesshrubsgrasslandcroplandartificial surfaceswater
September weather nearby: Chapadão do Sul 60 km · Mineiros 124 km · Alto Araguaia 137 km · Cassilândia 160 km · Jataí 166 km · Coxim 172 km · São Gabriel do Oeste 178 km · Rio Verde de Mato Grosso 185 km

Brazil travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / N
127 / 220 V · 60 Hz
Prices
≈ 46% of US
price level, 2025
GDP per capita
$10,713
2025
Happiness
6.6 / 10
World Happiness, 2025
Safe drinking water
89%
of population, 2024
Homicide rate
19.3
per 100k, 2023
Road deaths
16
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 482
Religion
Roman Catholic 57%Evangelical 27%none 9%other 4%

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 (-18.5439°, -53.1292°, elevation 646 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. 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).