Jacó weather in September
September in Jacó: sweltering, soaked, with clean air — a gamble, with 30 rainy days.
Updated September 2026 · climate normals from ERA5 reanalysis
#11 of 12 months in Jacó · #1199 of 1413 destinations to visit in September · comfort 56/100 (tier D)
- Days
- 28°C
- Nights
- 24°C
- Wet days
- 30
- Sun
- 7.6 h
- Humidity
- 89%
- Daylight
- 12 h

Traveller notes on Jacó in September
Notes from nearby Monteverde (81 km away)
Jacó doesn't have its own notes for September yet — these are about Monteverde, close enough to share the season.
Monteverde-forum threads on September describe this as genuinely deep in the region's off-season, a real tradeoff of fewer crowds against a much higher chance of unsettled conditions on a given day. Posters are consistent showers here often fall overnight rather than through the day, so a visitor can still get a clear, workable stretch for the canopy walks and reserve trails even during a heavier week overall. One short-stay visitor called themselves lucky with a genuinely beautiful couple of days despite planning around the reputation. Regulars describe the elevation as keeping things noticeably cool whenever the cloud cover thins, real layers worth having regardless of how warm San Jose or the coast felt on the same trip. Unpaved roads into town are called noticeably trickier this time of year, a higher-clearance vehicle a real asset. The record: 23.5C days feeling like 25C, 17.9C nights, an extraordinarily high 391mm across nearly 29 days and 90 percent humidity.
Other months in Jacó
Regulars are specific this area reads as genuinely drier than areas further south along the same coast, where the rainy season doesn't properly end until mid-to-late December, though conditions here have shifted from the old reputation of reliably rain-free North winds - even the tail end of the month can now bring real rain some years. Our row backs that hot, genuinely wet read, 27.6C reading as a scorching 33C, over 24C nights feeling 29C, with a substantial 278.6mm of rain across 28.5 days and humidity at 86 percent. Regulars are consistent Costa Rica's weather is genuinely location-dependent given how many separate weather systems affect the country, no single verdict applying evenly countrywide. The sea sits at a bath-warm 29.1C. The record: 9.9 hours of sun, a 9.7 kph wind and AQI 32.
The consensus on April for this coast is that it is transitional - not the driest, nowhere near the wettest - and our row proves it exactly: 242.9mm here against 581.8mm in May and 829.3mm in October. What the numbers cannot show is the timing, and the board supplies it: rain on the central Pacific coast comes in the afternoon or overnight, it is warm rain, and the weather apps that promise rain all day every day are wrong about the shape while right about the odds. Our 27.6 rainy days is that same statement. Pack fast-drying clothes rather than cotton, and something light to keep it off. Heat holds at 29.1C reading as 36C, with a 30.3C sea. The record: humidity 83 percent, 10.4 hours of sun and AQI 36.
January opens the hottest, driest run of the Costa Rican year, with strong sun and lower humidity - and regulars still say to expect some rain most days, generally in the afternoon or at night. Our 22.2 precipitation days across 120.4mm is that, five millimetres a day, and one visitor's accounting is the clearest version: roughly eight hours of rain across a week, five of them after dark. Their weather apps had predicted rain daily. The date worth knowing is the 6th: the first days of January are peak holiday travel, and waiting until after about then means the Christmas crowds have gone and prices ease, though it stays high season. A light poncho and a small umbrella cover it. The record: 28.4C over 24.4C reading as 34C, a 28.9C sea and AQI 33.
March is inside the driest and hottest stretch of the Costa Rican year, and our row's 19.7 precipitation days would say otherwise until you read the phrase regulars use: intermittent thunderstorms that do not produce much rain. That is 87.4mm spread across those days, under five millimetres each. Being socked in for days would be strange now; rain is always possible and rarely severe. What the dry season does bring is heat on the coast - 29.6C over a 25.4C night reads as 36C and 30C at 77 percent humidity, and with the Pacific at 29.9C there is nothing cool to get into. Their own figures, high 80s by day and mid 70s at night, match ours closely. The record: 11 hours of sun, a 12.4 kph wind and AQI 38.
Add your own note from Jacó's card on the map.
Jacó climate normals — September
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Jacó in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Quietschool holidays in 2 of the markets that fill it, one of its worst months for weather(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Jacó's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Toughest weatherJacó's weather peaks January–March, best around February.
Best weatherFair weatherToughest weather
What's on in Jacó in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Season
South swell season
1 Apr – 31 Oct · usuallySurf seasonThe southern-hemisphere swells arrive through the middle of the year. Playa Hermosa a few minutes down the coast is the serious wave and holds national contests; Jaco's own beach is where people learn.
- Season
Green season
1 May – 30 Nov · usuallyMonsoonMornings stay clear and the rain comes after lunch, hard and short. Rates drop by a third, the hills opposite turn over, and September and October are the two months that genuinely stay grey.
- Nature
Humpback whales
15 Jul – 15 Nov · usuallyWhale seasonSouthern-hemisphere humpbacks calve along this coast from July into November, which with the northern group arriving December to March gives Costa Rica one of the longest whale seasons anywhere.
- Nature
Olive ridley nesting
15 Aug – 15 Dec · usuallyTurtle nestingOlive ridleys nest on Playa Hermosa from August, heaviest through September and October, and the hatchery releases at dusk. The beach is patrolled at night and you go with the project or not at all.
- Season
Wet season
MonsoonRisk30 rainy days and about 720 mm in the month — the real kind of rainy season, not afternoon showers.
from the climate normals
Nearby, and something's on
Within 300 km of Jacó — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Jacó?
Jacó in September — FAQ
- Is September a good time to visit Jacó?
- September in Jacó: sweltering, soaked, with clean air — a gamble, with 30 rainy days. It ranks #11 of 12 months for Jacó on SeasonMap's comfort score (56/100).
- What is the weather like in Jacó in September?
- In September, Jacó averages a daily high of 27.7°C and a low of 24.3°C, with about 719.5 mm of rain over roughly 30 rainy days.
- What is the air quality in Jacó in September?
- Jacó has a mean US Air Quality Index of about 26 in September.
Within 300 km: Nosara's Arribada at Ostional around 1 Jul – 31 Dec, and Tortuguero's Green turtle nesting on 1 Jul – 31 Oct.