Weather in Guanacaste in December

How December compares

December is the 10th warmest month of the year in Guanacaste and ranks 11th of 134 destinations we compare for December - see where else is hot in December. Against London's average high of 7.7°C in December, Guanacaste is 21.4°C warmer by day and 19.7°C warmer at night.

Daytime and night-time in December

The typical December day in Guanacaste peaks at 29.1°C, but that is an average: the warmest 10% of days reach 30.9°C or more. About 100% of days top 25°C and 1 in 4 pass 30°C. Nights average 22.4°C; one night in ten drops to 21.3°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest December day here reached 33.3°C (2019-12-29) and the coldest night 18.8°C (2010-12-18).

Rain in December

Dry (3 rainy days or fewer): about 2 days with 1 mm or more, 14 mm in total. Year to year it varies a lot - the wettest December was 2016 with 84 mm, the driest 2004 with 0 mm. Humidity averages 76%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in December

The sea averages 27.2°C - warm enough to swim (22°c+). Depending on the year it ranges from 26.4°C to 27.9°C. For the warmest sea here, come in May (28.9°C).

Sunshine and daylight

Around 6.5 hours of sunshine a day (estimated from cloud cover), 11.4 hours of daylight: the sun rises about 05:52 and sets about 17:22 local time in mid-December. Average cloud cover is 43%.

Is December a good time to visit Guanacaste?

Yes - it is one of the better months: hot days, little rain. The best months for Guanacaste on our scoring are February, January, December; months averaging 25°C or more: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec.

Hot days, with little need for evening layers

Plan for lightweight, breathable clothes and a slower pace around midday. Humidity averages 76%, so the warmth can feel muggy, particularly when you are walking rather than sitting in the shade. Days reach 30°C on 24% of occasions, making hotter spells a realistic part of the trip rather than something to dismiss. Put more active plans earlier in the day and leave room for shade and swimming when the heat feels strongest. Average night lows of 22°C mean evenings generally remain warm, so heavy layers are not a priority. December suits you less well if cool nights are essential to feeling comfortable.

Mostly dry weather and comfortable swimming

Rain is unlikely to dominate your plans, with about 2 rainy days during December, though a completely dry stay is not guaranteed. There is about 6.5 hours of sunshine within 11.4 hours of daylight, so expect useful sunny stretches without assuming clear skies throughout the day. The sea averages 27.2°C, with a year-to-year range of 26°C to 28°C: comfortably warm for swimming rather than a bracing dip. That combination makes December a good fit for spending time by the water and keeping outdoor plans flexible. Pack sun protection as well as a light rain layer, but give hot-weather clothing most of the space in your luggage.