Q COSTA RICA — The Saharan dust, coupled with the presence of haze (a meteorological phenomenon consisting of very small particles of dust, sand, ash, or clay suspended in the atmosphere) and a significant reduction in rainfall, will cause a widespread deterioration in air quality in Costa Rica over the next few days.
The national weather service, the Instituto Meteorológico Nacional (IMN), forecasts that the most critical period will occur between Thursday and Friday, when the increase in particulate matter will impact almost the entire country and raise the risk of respiratory problems.
The concentration of particles will reach its highest levels mainly in the western part of the Central Valley, particularly in Alajuela and some areas of Cartago.
According to the IMN, the situation will improve significantly starting Saturday, when the dust cloud begins its movement toward other regions of Central America.
During the phenomenon, exposure to the polluted air can cause respiratory discomfort and exacerbate pre-existing conditions. Among the most vulnerable groups are children, the elderly, asthmatics, and allergy sufferers, who could experience symptoms such as asthma attacks, difficulty breathing, headaches, and allergic reactions if exposed for several hours.
IMN specialist Daniel Poleo explained that part of the dust cloud over the Caribbean Sea will enter Central America, increasing the particulate matter content in the atmosphere.
“Part of that dust cloud will reach the region, increasing the content of what we call particulate matter in the atmosphere,” the expert explained.
Although these particles may be imperceptible to the naked eye, their presence manifests as reduced visibility and a whitish or “milky” sky, a phenomenon known as haze.
Poleo pointed out that the dust will be present in almost the entire country, although the trade winds will concentrate larger quantities in specific regions.
Wearing a mask, reducing time spent outdoors, and stopping physical activity if symptoms appear are among the recommendations, even for people without respiratory illnesses.
Factors that aggravate the situation: particles, wind, and scarce rainfall
The phenomenon is due to a combination of factors. The particulate matter suspended in the air is composed of dust, soot, ash, pollen, and residue from burning or emissions.
In this episode, the Saharan dust contains especially fine particles, known as PM2.5, measuring 2.5 micrometers or less. Poleo emphasized that “they are respirable and quite harmful because, when they are smaller than 2.5 micrometers, they can reach the alveoli, which are the innermost part of the lungs.”
The risk does not come solely from the Saharan dust.
The force of the winds will also lift particles from the ground and carry pollen, while some burning in the region continues to contribute residue to the environment.
Official IMN weather forecast for Thursday, July 30, 2026:
This Thursday, trade winds in the Caribbean Sea will remain strong, generating wind gusts ranging from moderate (20 to 39 km/h) to strong (40 to 60 km/h) across the country, especially in mountainous areas.
At the same time, the presence of a mass of dry air over Central America is reducing humidity in the country, which promotes more stable atmospheric conditions. As a result, hot conditions will prevail during the day, along with very scattered and short-lived showers in the afternoon.