Weather in San Isidro in August

Shoulder season. August is shoulder season in San Isidro — cheaper, quieter, and a genuine gamble. You should expect rain on 26 days of the month, which is more days wet than dry.

August ranks 9 of 12 in San Isidro: past the worst of the year but short of February, which is the month to book if the dates are open.

Rain on 26 of the month's 31 days, 8 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 88% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average August reaches 30 °C; the day barely swings — 5.3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest August day reached 29.4 °C and the coldest night fell to 18.7 °C, and the wettest single day dropped 67 mm — roughly 30% of the month's rain in one day.

August is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest August on record still delivered 353 mm against 89 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 226 mm average is a reasonable planning figure, not a promise.

Wind is light at 1.6 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 88% is the real story though — it is the number that decides how the day feels, not the 26.5 °C.

How August sits in the year

Temperatures hold steady either side: 26.4 °C in July, 26.5 here, 26.4 in September. Nothing about the timing within the month matters much.

Daylight in August

San Isidro sits close enough to the equator that daylight barely moves all year — 12.4 hours in August, against a range of just 1.1 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

An inland climate

Despite being inland, the year stays fairly even: 9.3 °C between the year's warmest afternoons and coldest nights. At 713 m the air is thin enough to matter — sun that burns faster than the temperature suggests, and nights that cool off quickly.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

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

August in San Isidro versus nearby

If San Isidro is one option among several, the nearby comparison is worth making. San José is close enough to be a coin toss — 2.6 °C cooler, 2 days less rain. Limón is close enough to be a coin toss — 2.2 °C warmer, 3 days more rain.

So: August works, with February the better month by 18 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in San Isidro

See all twelve months in San Isidro, or where else to go in August.