Between the dry and wet seasons in Costa Rica, a transition period occurs when rainy and dry days alternate. A typical forecast for late April in the Central Valley might read:
Mornings clear, with few clouds. Afternoons partly cloudy, with isolated rainfall. Temperatures warm, with a lot of haze.”
Meteorology, the science dealing with the atmosphere, weather, and climate, falls under the domain of the National Meteorological Institute, part of the Ministry of Environment and Energy (MINAE).
Meet Werner Stolz
Werner Stolz, 41, is the head of analysis and prediction management at the institute. Born in Honduras, Stolz studied physics and meteorology at the Autonomous University of Honduras and the University of Costa Rica. He has lived and worked in Costa Rica for over a decade.
“Meteorology is a living science,” says Stolz. “It’s not just theory; it has an important application in society.”
Collecting Data to Predict the Weather
Stolz and his team of five meteorologists and three technicians evaluate data from approximately 400 weather stations across Costa Rica, 14 satellite stations, and international services such as the U.S. National Hurricane Center.
Each morning, a radiosonde is launched from the institute’s weather bureau in Alajuela, providing critical atmospheric data. The information is analyzed using computer-based programs and shared with the public through various channels, including the institute’s official website.
The Role of the National Meteorological Institute
The institute provides critical weather forecasts for various sectors, including aviation, emergency services, agriculture, tourism, and utility providers. Weather bureaus are maintained in Puntarenas and all four international airports in Costa Rica.
Costa Rica’s Climate and Seasonal Patterns
Costa Rica experiences two primary seasons:
- Rainy Season: May to November
- Dry Season: December to April
On the Caribbean side, the driest months are March and September. The country’s weather is shaped by its position near the equator and the orientation of the Central Mountain Range, which divides the country into two climatic zones.
While temperature fluctuations are minimal throughout the year, precipitation varies significantly. The southern Pacific, northern Caribbean coast, and parts of the Central Mountain Range are the wettest areas, receiving over 4,500 mm (180 inches) of annual rainfall. In contrast, the northwestern lowlands are the driest.
Key Weather Influencers
Weather changes in Costa Rica are influenced by the trade winds, polar fronts, hurricanes, and the Intertropical Convergence Zone (ITCZ).
- ITCZ: A climatic “heat engine” located around the equator, responsible for 60% of Costa Rica’s annual rainfall.
- Veranillo: A “little summer” period of reduced rainfall during the rainy season.
- Nortes: Strong winds and cooler weather during December and January caused by cold polar air.
By understanding Costa Rica’s weather patterns and the factors that influence them, residents and visitors alike can better prepare for the unique climate challenges and opportunities the country presents.
