Weather Warning

Increased rainfall in the Pacific

June 12, 2025

10.00 a.m.

Discussion: The Intertropical Convergence Zone is beginning to strengthen off the Pacific coast of Costa Rica, increasing the intensity of the moisture flow entering from the oceanic sector toward both sides. This morning, partly to completely cloudy conditions prevail across the country, and convective nuclei are observed moving from the Pacific Ocean toward the South and Central Pacific coasts.

Forecast: Scattered showers and a possible thunderstorm are expected late this morning in the South and Central Pacific regions of the country, including the Nicoya Peninsula. Dense cloud cover is expected this afternoon, giving way to more consistent and widespread rainfall in the Pacific regions, with estimated amounts of 10 to 50 mm (0.4 to 2.0 in), with peak rainfall of 60–100 mm (2.4–3.9 in) over a period of 6 to 12 hours. Light to moderate rainfall and fog are projected for the Central Valley, with accumulated amounts of 20–40 mm (0.8–1.5 in) over a period of 6 to 12 hours. Isolated but heavy showers are expected in the northern region and Caribbean mountains, with amounts of 30–60 mm (1.2–2.4 in) and possibly higher amounts in localized areas. Lowland areas will experience scattered showers.

There is a high possibility of continued rainfall throughout the night in the North Pacific and the Central and South Pacific coasts. The possibility of light rain and fog banks cannot be ruled out in the Metropolitan Area.

⚠Note: Analysis and numerical models continue to indicate an increase in rainfall for at least the next 2-3 days (with the possibility of further extension), especially on the Pacific side. This is due to the strengthening of the Intertropical Convergence Zone, the passage of OT#5 on Friday, and the possible formation of a low-pressure system in the Pacific near the country over the weekend. The IMN will continue to monitor these systems and provide a forecast update as appropriate.

Warning: Special attention should be paid to the Nicoya Peninsula, the Sarapiquí Basin, and the South Pacific, as these areas have very high soil saturation levels of 85-95%, increasing the risk of incidents.

Due to the above, the IMN recommends:

• Caution due to sewer saturation in areas prone to this type of flooding.
• Prevention in the event of a thunderstorm and seeking shelter in a safe place in the event of strong wind gusts occurring or perceived near storm clouds, due to the possible fall of tree branches, power lines, among other things. These gusts can reach 80 km/h in some isolated cases.
• Stay informed through social media: Twitter: @IMNCR, Facebook: Instituto Meteorológico Nacional CR, and the website: www.imn.ac.cr

Rebeca Morera R
Meteorologist/DMSA-IMN