Weather conditions are expected to be pretty variable for the next seven days, with high humidity and instability bringing heavy rainfall at the beginning of the week, followed by more stable and less humid conditions from midweek to the end of the week.
Today (Monday) marks the passage of Tropical Wave #22 and along with the position of the International Convergence Zone, that means a higher probability of rain and heavy downpours. This rain is most likely to occur in the western part of the North Caribbean, the Northern Zone, South Pacific, the mountains and coasts of the Central Pacific, and the Nicoya Peninsula.
As I write this forecast this Monday evening, we’re already seeing these conditions in action. Here on the Central Pacific we are getting some heavy thunderstorms with off-and-on downpours. Santa Cruz in Guanacaste has been getting walloped high-intensity downpours/thunderstorms for over an hour, with accumulated rainfall exceeding 100 mm (nearly 4 inches). This gives you a real-time example of what the Tropical Wave and Convergence Zone are capable of!
Tuesday we will see the Convergence Zone and its low pressure continue to bring showers and thunderstorms to the Pacific slope, Central Valley, and parts of the Northern Zone.
Luckily, starting Wednesday, conditions shift again. Another period with canicular characteristics is expected with decreasing humidity, gradually increasing trade winds, and the approach of a dry air mass with fresh Saharan dust (these characteristics start to become more pronounced between Thursday and Friday). That means more isolated rainfall for the Pacific slope and only occasional showers for the Caribbean slope.
Monday-Tuesday active period: The most intense rainfall of the week with Tropical Wave #22 and Convergence Zone effects bringing widespread heavy downpours and thunderstorms.
Wednesday transition day: Humidity begins decreasing and trade winds start strengthening as the active weather pattern weakens.
Thursday-Friday dry dominance: Peak canicular conditions return with Saharan dust influence, strong trade winds, and very scattered rainfall across most regions.
Weekend stability: Continued dry, stable conditions with only isolated shower activity.
Few to partly cloudy conditions for both Pacific and Caribbean regions. Unstable coastal areas of the Pacific will experience isolated showers near the coasts during the first two days of the week. Variable clouds with possible occasional rain showers will affect the Caribbean side on Wednesday, Saturday, and Sunday.
The Pacific and Central Valley regions will be mostly cloudy with rain accompanied by thunderstorms on Monday and Tuesday (the most active period). The remaining days will see increasingly scattered showers and occasional thunderstorms for the Pacific side, mainly affecting the Central and South Pacific.
Moderate to strong winds will develop from Thursday onward over the Central Valley and North Pacific as trade winds strengthen. The Caribbean and Northern Zone will have partly cloudy afternoon conditions with possible occasional showers in western areas and over mountains, mainly during the last three days of the period.
Cloudy to partly cloudy conditions in Pacific regions, with possible showers and rain in western Pacific and coastal areas during the first three days of the week. Activity becomes more isolated as we move into the second half of the week. The Caribbean and northern Pacific will be partly cloudy with scattered showers.
Central Valley & North Pacific: Experience dramatic changes this week, starting with intense thunderstorm activity Monday-Tuesday, then transitioning to windy, dry canicular conditions Thursday-Friday with moderate to strong trade winds.
Caribbean & Northern Zone: See the most consistent pattern with occasional showers throughout the week, though activity increases slightly during the final three days as atmospheric patterns stabilize.
Central & South Pacific: Bear the brunt of early-week storm activity, then settle into typical canicular patterns with scattered afternoon showers becoming increasingly isolated.
Temperature patterns will shift from comfortable during the active period to hot as dry air and Saharan dust influence takes hold mid-week. Especially in Guanacaste!
Here’s what we are looking at for high and low temperatures across Costa Rica’s different regions:
High: 31° (87.8°) | Low: 15° (59°)
High: 36° (96.8°) | Low: 18° (64.4°)
High: 32° (89.6°) | Low: 16° (60.8°)
High: 33° (91.4°) | Low: 18° (64.4°)
High: 30° (86°) | Low: 16° (60.8°)
High: 32° (89.6°) | Low: 17° (62.6°)
This forecast is based on the weekly outlook shared by Costa Rica’s National Meteorological Institute (IMN).
