Weather in Guanacaste in August

How August compares

August is the 6th warmest month of the year in Guanacaste and ranks 44th of 134 destinations we compare for August - see where else is hot in August. Against London's average high of 21.4°C in August, Guanacaste is 8.4°C warmer by day and 9.5°C warmer at night.

Daytime and night-time in August

The typical August day in Guanacaste peaks at 29.8°C, but that is an average: the warmest 10% of days reach 31.9°C or more. About 100% of days top 25°C and 1 in 2 pass 30°C. Nights average 23.0°C; one night in ten drops to 22.0°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest August day here reached 34.9°C (2019-08-02) and the coldest night 20.2°C (1996-08-29).

Rain in August

Wet (more than 8 rainy days): about 20 days with 1 mm or more, 216 mm in total. Year to year it varies a lot - the wettest August was 2010 with 691 mm, the driest 1997 with 17 mm. Humidity averages 84%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in August

The sea averages 28.7°C - warm enough to swim (22°c+). Depending on the year it ranges from 28.3°C to 29.1°C. For the warmest sea here, come in May (28.9°C).

Sunshine and daylight

Around 2.0 hours of sunshine a day (estimated from cloud cover), 12.4 hours of daylight: the sun rises about 05:32 and sets about 18:00 local time in mid-August. Average cloud cover is 84%.

Is August a good time to visit Guanacaste?

It is a reasonable choice: hot days but expect showers. 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, warm seas and little overnight cooling

The heat is dependable, but humidity makes it less comfortable for active days. At 84% humidity, loose, breathable clothes are a better choice than heavy fabrics, and strenuous plans are best kept away from midday. Hotter days can reach around 32°C or more, so cloud cover is no reason to leave sun protection behind. The sea averages around 29°C, making swimming appealing if you dislike a chilly entry, though it will offer less cooling than a cooler sea. Nights average 23°C, so do not expect much relief after sunset. Light evening clothing and accommodation with effective cooling should make the warmth easier to manage.

Plan around rain, not guaranteed sunshine

August is a wet month, with about 20 rainy days, so it is a poor fit for a holiday built around uninterrupted time outdoors. That does not mean every wet day is a complete washout, but there is no basis for counting on a fixed dry window each day. Sunshine averages only about 2 hours within 12.4 hours of daylight: there is plenty of daytime, but relatively little bright sun. Pack a lightweight waterproof and a waterproof bag for essentials, and leave room to rearrange outdoor plans. This month works better for travellers who are content with warmth, cloud and pauses for rain than those seeking dependable sunbathing weather.