Weather in San Isidro in December

Shoulder season. December sits in between. You will get good days and you will lose some. You should expect rain on 19 days of the month, which is more days wet than dry.

December ranks 6 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 19 days, 4 of them heavy. Enough to need a plan B, not enough to need a plan around it. 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: it never really gets hot: not one day in an average December reaches 30 °C; the day barely swings — 5.6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 28.4 °C and the coldest night fell to 16.1 °C, and the wettest single day dropped 95 mm — roughly 63% of the month's rain in one day.

December is moderately variable: 44 mm in the driest year against 342 mm in the wettest, around an average of 150 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 1.5 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 26.1 °C.

How December sits in the year

Temperatures hold steady either side: 25.7 °C in November, 26.1 here, 26.4 in January. Nothing about the timing within the month matters much. Rain is the thing that moves: January brings 6 days less of it, so pushing the dates later buys drier weather.

Daylight in December

San Isidro sits close enough to the equator that daylight barely moves all year — 11.6 hours in December, 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

Shoulder. The value months — prices ease off and you get the place closer to itself.

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

December in San Isidro versus nearby

If San Isidro is one option among several, the nearby comparison is worth making. San José is a better bet in December — 2.4 °C cooler, 5 days less rain. Limón is close enough to be a coin toss — 2 °C warmer, 4 days more rain.

So: December works, with February the better month by 15 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 December.