Each year in the middle of Costa Rica’s rainy season, Ticos living in Guanacaste, Puntarenas and parts of Alajuela await a respite from the afternoon downpours that are expected May through mid-November. These breaks from the rain are called “veranillos,” or “little summers.” (In the U.S. there is a similar phenomenon that happens in late autumn called “Indian Summer.”)

But are these Costa Rican “little summers” folkloric tales, or are they phenomenons based upon science?

The answer: a little bit of both.


Patricia Ramirez, at the Meteorological Institute of Costa Rica, analyzed 40 years of data spanning from 1941 to 1980 looking for weather patterns. In an investigative study that she published for the Ministry of Farming and Ranching, Ramirez noted that “the Veranillo occurs almost every year – but the exact period of this absence of rain varies from year to year, both in start date and duration.” These breaks from the rain happen in strings of dry days lasting anywhere from 3 to 15 or more days.

Interestingly enough, Ramirez also found that “the decrease in precipitation that occurs on the Pacific side of the country coincides with a relative maximum rainfall on the Atlantic side.” In other words, Costa Rica’s Caribbean coast absorbs all of the rain for us during these dry periods as we enjoy sunshine here in Guanacaste.

Ramirez’s paper also talks about how these “little summers” come in three somewhat predictable parts.

The first part is “El Veranillo de San Juan,” or the “Little Summer of San Juan.” This falls around June 23rd, when Latin America celebrates La Noche de San Juan (St. John the Baptist). According to Roman Catholics, Saint John the Baptist was born on June 24th – just 6 months before Jesus Christ.

However, El Veranillo de San Juan is less of a blessing from St John the Baptist and more of a meteorologic phenomenon that has to do with mountain ranges, wind patterns and cold fronts within Costa Rica. On a macro scale, El Veranillo de San Juan also interrupts rainy season in several other Central and South American countries (including Nicaragua, Argentina, Paraguay, Chile, and Uruguay). I’ll spare you from the boring details and suffice it to say that this all seemingly happens thanks to subantarctic cold fronts that are blocked from reaching the north. This crazy weather could also have something to do with the fact that it coincides with June 21, the summer solstice in the Northern Hemisphere and the winter solstice in the Southern Hemisphere.

We’ve accounted for the first major veranillo – now onto the latter two, which are much less exciting. La Primera Canícula, or the “First Dog Days,” is the second veranillo that typically occurs at the end of July. The third dry spell called La Segunda Canicula, or “The Second Dog Days,” tends to happen in early August.


So when are you most likely to have a “Little Summer” during rainy season in Costa Rica?

Based upon this study, the most intense dry periods fell most frequently between July 12 and August 14th. During this period, the probability of an occurrence of an Indian Summer is greater than 50%. However, take this with a grain of salt – the research only covers 1841-1980, and it does not take into consideration the years between 1980 and now.

Photo credits: Genna Marie of Tamarindo Family Photos