The Intertropical Convergence Zone (ITCZ) becomes the dominant weather driver over the next seven days, bringing rainy conditions nationwide. This powerful meteorological feature, where trade winds from both hemispheres meet and create persistent thunderstorm activity, will be extra active throughout the coming week.
Understanding the ITCZ: This weather-making system plays a crucial role in Costa Rica’s climate patterns, especially as we head into the heart of rainy season in September and October when it typically exerts its strongest influence over most of the country. Learn more about how it works and why it’s so important in our detailed guide to Costa Rica’s Intertropical Convergence Zone.
This Thursday, the ITCZ has become particularly energized following the passage of Tropical Wave #26, creating widespread cloudy and rainy conditions throughout the country. The combination of these two systems establishes an atmosphere primed for more precipitation.
Extended Active Weather Ahead
More intense rainfall conditions are projected to continue throughout the entire seven-day forecast, representing a sustained shift toward very active weather patterns. Looking ahead, Tropical Wave #27 approaches early next week, setting up what could be a highly unstable start to September.
Important Note for Travelers and Residents: While we’re forecasting rainier overall conditions, this doesn’t mean constant downpours. Costa Rica’s weather patterns typically feature pleasant morning windows with afternoon and evening storm development. Plan outdoor activities for morning hours when conditions are generally most favorable.
Thursday’s ITCZ activation: Todays enhanced rainfall activity was a result of the convergence zone, amplified by Tropical Wave #26’s recent passage.
Friday-Sunday sustained activity: The ITCZ maintains its dominant influence, creating consistent afternoon and evening thunderstorm development across most regions.
Early September transition: Tropical Wave #27’s approach sets up potentially intense weather patterns as we enter a new month.
Partly cloudy skies typically develop across Pacific regions and the Central Valley, offering the best weather windows for outdoor activities and travel.
Limón and the Northern Zone may see some rain and shower development, morning hours generally provide the most stable conditions of each day.
The Central Valley and Pacific regions transform from partly cloudy to cloudy conditions as heating builds atmospheric energy, triggering showers and thunderstorms.
The Caribbean and Northern Zone experience variable cloudiness with enhanced rainfall concentrated in mountain areas where the ITCZ’s effects are amplified by terrain.
North Pacific and Central Valley areas maintain partly to completely cloudy conditions with possible rain extending into early nighttime hours.
Limón and northern regions see continued shower activity.
Central and South Pacific coastal areas experience the most consistent evening storm activity with showers developing along the coastline.
Pacific Regions and Central Valley: Experience the classic ITCZ-driven pattern of morning clearing followed by afternoon thunderstorm development. The convergence zone’s influence creates more widespread storm coverage than typical local heating patterns.
Caribbean and Mountain Areas: See enhanced rainfall as the ITCZ’s moisture-rich air interacts with elevated terrain, creating orographic lifting that intensifies precipitation over mountain ranges.
Coastal Zones: Both Pacific and Caribbean coasts experience extended evening storm activity as the ITCZ maintains atmospheric instability well past typical daytime heating cycles.
Temperatures remain moderated by increased cloud cover and storm activity, though morning warming still occurs during clearer periods.
High: 30° (86°) | Low: 15° (59°)
High: 35° (95°) | Low: 20° (68°)
High: 32° (89.6°) | Low: 15° (59°)
High: 32° (89.6°) | Low: 19° (66.2°)
High: 32° (89.6°) | Low: 14° (57.2°)
High: 32° (89.6°) | Low: 16° (60.8°)
This forecast is based on the weekly outlook shared by Costa Rica’s National Meteorological Institute (IMN) and other sources.
