Weather in Costa Rica

Costa Rica’s Weather Overall

Costa Rica lies firmly in the Neotropical zone, just a few degrees north of the equator, in that region where day length varies little and the sun is directly overhead at noon twice each year, rather than once as in the northern hemisphere. As a tropical nation, its climate is one of year-round warmth, but there is still a sharp divide between the dry season and the wet season. The dry season is generally sunny and has little rain, while the wet season still includes abundant sunshine but is also marked by plenty of rain, from afternoon showers to lasting deluges.

The thick jungle that covers much of Costa Rica is a product of the two factors of everlasting warmth and huge amounts of moisture. Even in the dry season, for example, the trade winds blow from the northeast, and their humidity condenses out as thick mist as the air ascends the mountain slopes. This leads to the formation of dense cloud forest at higher elevations on the eastern side of the mountain cordillera.

To sum up, Costa Rica’s weather is warm to hot, and generally anywhere from humid to actually wet. The Pacific coast witnesses drier conditions, but this term is relative, and if you visit Costa Rica, you should expect the warmth, humidity, and rich spicy plant smells of a tropical greenhouse.

Weather of Alajuela Province

Most of Alajuela Province, which is located in the northwest interior of Costa Rica and borders on Nicaragua, is part of what is known as the North Pacific region of the country, though part of the Central Valley is included in Alajuela, as well. The province is quite hot, though the nights during the dry season (when there is little or no insulating cloud layer) can be cool despite the hot days. Rainfall varies from miniscule to moderately heavy, depending on the season.

May, June, July, August, September, and October are the rainy season in Alajuela Province – a relatively short period compared to the longer wet season along the Caribbean. The relative humidity is 80% to 85% during this time even in sunny weather, and the daytime temperatures are 87º to 89º F (31º to 32º C), making the rainy season rather steamy in Alajuela. Overnight lows are a mildly warm 71º F (22º C).

Rainfall in the wet season starts at around 3” per month, rising to 10” per month by June, slackening to 5” per month in July, and increasing to 12” per month in September and October before the rains cease. Sunlight averages six to seven hours per day during the rainy season, with afternoon rain or storms providing most of the moisture. The rain is typically windless and the period is noted for its calm.

The dry season is parching at times, with rainfall always less than 1” and often as low as 0.02” per month. The temperatures are higher than in the rainy season, with 91º F (33º C) representing the average and those as high as 100º F (38º C) occurring fairly often. Sunshine is everywhere at this time, with over ten hours per day on average. The winds are light, at around 7.5 miles per hour, and come from the northeast – trade winds from the distant Caribbean. Lake Arenal, the largest lake in Costa Rica, has winds of up to 40 mph on its surface, however, making it popular for windsurfing.

Weather of Cartago Province

Cartago Province, located in the high Central Valley of Costa Rica and filled with many mountains, has a climate and set of annual weather patterns far different from the humid heat of the eastern coast, or the dry heat of the western. The weather here is mild thanks to the elevation, humid throughout the year, and features light to moderate rainfall by the standards of Costa Rica (though total rainfall per month in the rainy season is still very high when considered from a temperate viewpoint).

The rainy season and begins in May in the high folds of Cartago Province’s uplands and continues through October, though considerable rain also falls in November as the wet season tapers off. 7” of rain per month fall in May in June, while July is somewhat drier with only 5 inches of rain. The rainfall then picks up and may get as high as 9” to 10” per month in September and October before the dry season arrives. During this period, mornings are usually pleasantly sunny, followed by rain in the afternoons. Winds are usually low during this period.

The dry season is windy and extremely sunny, especially in January, February, and March, with brilliant sun throughout the day except on the high peaks, where cool mists may last through much of the daylight hours, allowing the growth of cloud forest. Rainfall is generally less than 1” per month during this time, though the early dry season witnesses slightly higher rainfalls (particularly November, when 4” of rain falls on average).

Since the temperature and humidity combination is more an artifact of altitude than of the oceans in Cartago Province, they remain fairly constant throughout the year. High temperatures range from 73º to 79º F (23º to 26º C) throughout the year, with May tending to be slightly warmer with the start of the annual rains.

Weather of Guanacaste Province

Guanacaste Province is one of the driest provinces of Costa Rica, lying as it does along the northwestern Pacific coast of the nation, away from the prevailing trade winds off the Caribbean. This area is covered densely in dry tropical forest, which features many flowers during the dry season. The landscape turns verdant, emerald green during the wet season, however, so both periods of the year have something to recommend them to the avid ecotourist.

The eastern edge of Guanacaste Province is hedged by a range of volcanoes forming two cordilleras, de Guanacaste and de Tilaron. These mountains are swathed in eternal greenery because they are high enough to condense large amounts of mist out of the rising air climbing their flanks, sustaining a thick growth of cloud forest. Their weather is cool and damp year round, so if you need an escape from the dry season heat, try a hike in the volcanic national parks here.

May through October is the rainy season in Guanacaste, with calm or very light winds and two peaks of rainfall, one in June (around 10”) and one in October (around 11”). July is the driest month in the rainy season with roughly 6” of rain at the province’s capital, Liberia.

November, December, January, February, March, and April are the dry season and experience dry heat that is the signature of this province. This is the favorite beach season for tourists and is also the time when many flowers appear in the otherwise fairly desiccated dry tropical forest. Daytime temperatures average around 95º F (35º C) and may climb to 100º F (38º C) a number of times during the half-year dry season.

Overnight lows at the start of the dry season are a baking 89º F (32º C), though these descend to a refreshing 69º F (21º C) as the season progresses. Humidity drops as low as 60% during this period, and rainfall is around 0.04 inches (1 millimeter) per month, though this increases slowly as the wet season approaches.

Weather of Heredia Province

Heredia Province straddles several different climatic zones, and its weather is therefore fairly complex. It is located in the north central area of Costa Rica and consists of basically two sections – a northern plain, which is the agricultural breadbasket of the nation, and the southern section which includes mountainous terrain and part of the Central Valley. The northern plains area tends to be hot and windless, while the southern highlands are cool and somewhat windy.

The rainy season sees hotter temperatures in the lowlands, with 85º F (30º C) as the average daytime high in these areas, with the rains, as usual, lasting from May through November. The highlands are startlingly cooler during this period, with daytime highs of 70º F (21º C) being the average. Lowland lows average 68º F (20º C) and highland overnight lows 55º F (9º C). Unlike other areas of Costa Rica, rainfall peaks in July (whereas July is the driest month of the rainy season in other provinces) at 19”, while rainfall as a whole varies from 10” to 19” monthly at this time.

The dry season is cooler than the wet season, though only by a degree or two. Unusually, the dry season is nearly as wet as the rainy season in this province, with up to 7” of rain falling per month, though this comes as heavy showers interspersed with brilliant sunshine rather than the grey, damp days of northerly climes. The driest month is April, when only 3” of rain falls on average. Winds are slightly stronger in the dry season than when the rains are falling.

Weather of Limon Province

Limon Province occupies the coastal lowlands at the northern end of Costa Rica’s Caribbean coast, and the weather here is naturally strongly influenced by the adjacent sea. There are no clear cut rainy and dry seasons, with heavy rain year round except for a few scattered months.

However, just because rainfall totals 141” per year on average does not mean that there is a lack of sun. Most days are sunny with a brief but possibly heavy rain in the afternoon, so there is plenty of opportunity for everything from hiking and bicycling to sunbathing and surfing. The rain is also not the bitter, wind-driven type found in the northern hemisphere, but is warm and usually unaccompanied by wind.

Temperatures are constant year-round, with 85º to 88º F (30º to 31º C) being the norm during the day, and nighttime hours witnessing temperatures of 69º to 71º F (21º to 22º C). Rainfall varies from 10” to 15” monthly, with the exceptions of February and March, and September and October, which are somewhat drier. The rainfall in these months is anywhere from 5” to 8”, or about half what the precipitation is in other months.

Weather of Puntarenas Province

Puntarenas Province occupies the southern two thirds of Costa Rica’s Pacific coast, stretching along a narrow seaside strip for much of its length before expanding inland just north of the Panamanian border. Most visitors to the nation’s western coast visit here and many of the most interesting mangrove forests grow along this stretch of shore due to the relatively high rainfall. The area is hot, humid, and wet, and experiences more rain and a shorter dry season than the northern end of the coast.

May, June, July, August, September, October, and November constitute the wet season proper, and rainfall may rise as high as an astonishing 27” per month during this period. Rainfall is heaviest towards the culmination of the rainy season, and July tends to be somewhat drier than the other months (and definitely has more sun than the main wet season months).

Relative humidity is close to 90% during this period. Average high temperatures are 87º to 90º F (31º to 32º C) by day, while lows dip to 71º to 72º F (22º C) overnight. April and December are transitional between the rainy and dry seasons, with around 11” of rain per month.

The short dry season is slightly hotter than the wet season, with typical temperatures of 91º F (32º C) in the afternoon and 73º F (23º C) after nightfall. The humidity falls to a “mere” 75% during this time, though it may range higher at some locales. Puntarenas Province, in short, is hot and humid, unlike the hot, dry conditions common in the northern Pacific area of Costa Rica.

Weather of San Jose Province

San Jose Province is literally central in the country, occupying the high Central Valley and housing more than a third of all the people who dwell in this tropical land. The “Eternal Spring” that the inhabitants speak of is a reality, though it is a rather warm spring by European or American standards. Due to its elevation, temperatures are mild throughout San Jose Province throughout the year, though there is still a distinct wet and dry season cycle.

The rainy season encompasses May, June, July, August, September, and October, lasting almost precisely for half of each year. Average monthly rainfall varies from 8” in May and July to 13” in September and October – though this is considerably less than many of the other provinces of Costa Rica. Temperatures are warmest in the wet season, climbing to 77º or 78º F (25º or 26º C) on average during these rainy months. Winds tend to be weak in this period, humidity high, and sunshine strong in the morning with showers or thunderstorms in the afternoon hours.

The dry season is cool on average, with diurnal temperatures of 73º F (23º C) and nocturnal lows of 59º F (15º C). Humidity is a bit lower, but still very high and moist, while winds pick up somewhat from the northeast. There is a lot of sun daily and rains tend to be brief. The driest month is February with 0.24” of rain and probably the most ideal, refreshing weather on the planet at that time.

For more information about the topic see Costa Rica Climate article.