Weather in Puntarenas in September

A hard month. September is a hard month in Puntarenas, and worth planning around. You should expect rain on 26 days of the month, which is more days wet than dry.

September ranks 9 of 12 in Puntarenas: past the worst of the year but short of December, which is the month to book if the dates are open.

Rain on 26 of the month's 30 days, 9 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Natural fibres and a second shirt for the day. At 85% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 15 days top 30 °C — hot spells arrive, but they break; the day barely swings — 4.4 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 34.9 °C and the coldest night fell to 24 °C, and the wettest single day dropped 97 mm — roughly 37% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 411 mm against 66 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 259 mm average is a reasonable planning figure, not a promise.

Wind is light at 6.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 85% is the real story though — it is the number that decides how the day feels, not the 30 °C.

How September sits in the year

Temperatures hold steady either side: 30.8 °C in August, 30 here, 29.3 in October. Nothing about the timing within the month matters much.

Daylight in September

Puntarenas sits close enough to the equator that daylight barely moves all year — 12.2 hours in September, against a range of just 1.2 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

Sea temperature

The sea sits at about 28.3 °C in September — warm enough that the water offers no relief from the heat. The sea peaks at 29.5 °C in April and bottoms out at 27.7 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Puntarenas versus nearby

If Puntarenas is one option among several, the nearby comparison is worth making. San José is a better bet in September — 6.7 °C cooler, 1 day more rain. Liberia is close enough to be a coin toss — within a degree on temperature, 2 days more rain.

So: September is a compromise. December is 23 points better and is what Puntarenas is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Puntarenas

See all twelve months in Puntarenas, or where else to go in September.