IMN Forecasts Afternoon Storms for Central Valley and Pacific Slope Ahead of a Drier Week

The IMN predicts afternoon thunderstorms for the Central Valley and Pacific slope today, April 27, 2026, followed by a dry spell as the seasonal transition continues.

By: AXL Media

Published: Apr 27, 2026, 10:40 AM EDT

Source: The Tico Times

Afternoon Rainfall Pattern and Localized Storms

According to the latest report from the Instituto Meteorológico Nacional (IMN), moisture levels remain high enough to trigger localized convective activity today. While the country experienced heavy rainfall over the weekend, today's moisture feed is expected to be more concentrated. The IMN forecasts that the most active weather will occur during the afternoon hours, specifically targeting the western Central Valley, the Central Pacific, and the Guanacaste region. Residents in these areas should prepare for sudden downpours and isolated electrical storms.

Regional Variations: Dry Skies in the Caribbean and North Zone

While the Pacific side prepares for rain, the Caribbean coast and the North Zone are expected to remain largely dry. Forecasters indicate that partly cloudy skies will dominate these regions throughout the day and evening. This regional dichotomy is a standard feature of Costa Rican meteorology during the seasonal transition, where the Caribbean influence often keeps the eastern half of the country drier even as the Pacific slope begins its descent into the rainy season.

Temperature Outlook: From Mountain Cool to Coastal Heat

Today's forecast highlights the extreme microclimates of Costa Rica. The North Pacific remains the hottest part of the country, with Nicoya expected to reach a sweltering 37.0°C (98.6°F). In contrast, mountain towns like Heredia and Cartago will enjoy significantly cooler temperatures, with daytime highs staying below 28°C and evening lows dropping as far as 14.0°C (57.2°F). This sharp thermal contrast remains a defining characteristic of the Central Valley vs. coastal provinces.