If you have outdoor plans today, you have a decent window — but it closes in the afternoon on the Pacific side, and the bigger item is still a day or two out. The Instituto Meteorológico Nacional forecasts a manageable Sunday, with rain concentrated at the edges of the day in the Caribbean and Northern Zone and heavier downpours building over the Pacific after lunch.
Tropical wave No. 35 is expected to reach early next week. It will land on ground that has already absorbed a month of rain. Start with today, in the Caribbean and Northern Zone, expect cloud and scattered rain through the early morning. Conditions ease by midday, leaving partly cloudy skies with rain holding to the mountains through the afternoon. Both regions see rain pick up again after dark.
The Pacific runs the opposite pattern as mornings are largely clear, then storms build. The IMN expects downpours with thunderstorms across the Nicoya Peninsula, the Central Pacific and the South Pacific through the afternoon, with rain lingering along the coast into the first hours of the night.
In the Central Valley you get few clouds to partly cloudy through the morning, possible drizzle to the east, then scattered afternoon rain and light rain or drizzle overnight. San José tops out around 26.2°C (79°F), Cartago around 24.5°C (76°F). Guanacaste is the outlier. It stays hot, dry and windy — Liberia reaches 37.6°C (99.7°F) and Nicoya 37.1°C (98.8°F), with few clouds and scattered showers confined to the peninsula in the afternoon.
Wind is the thing to plan around today as the IMN forecasts occasional gusts between 20 and 50 km/h (12 to 31 mph), with maximums reaching 80 km/h in the mountains and northern Guanacaste, and to a lesser extent toward the Central Valley. That top figure works out to about 50 mph, which is enough to bring down branches and put loose debris in the road. If you are driving an exposed ridge route or anything high-sided, that is the number that matters more than the rain.
The forward-looking concern is what happens when wave No. 35 arrives. The IMN’s weekly outlook places it at the start of the week and points to increased instability alongside it. In a bulletin issued yesterday, the institute indicated the wave could reach us before dawn tomorrow, though today’s regional forecast does not restate that timing.
What makes this wave worth watching is not its strength but where it lands. In yesterday’s bulletin the IMN flagged soil saturation between 80 and 90 percent in the Caribbean Norte and Northern Zone basins. Ground that is already close to full cannot take much more since rain that would normally soak in instead runs straight off the surface and into rivers and storm drains, which is why a moderate rainfall can produce a sharp river rise in these areas while the same rain does nothing much elsewhere.
That is the mechanism behind the flooding that displaced hundreds of people across SarapiquÃ, Limón and the Northern Zone earlier this month, and it has not reset. The IMN also asked for caution in urban areas, where drainage systems can back up under the same conditions.
If you are going to the Caribbean, Route 32 deserves a check before you leave rather than after. The highway between San José and Limón has closed repeatedly this month when material comes down in the mountainous section, and the closures are not always announced far in advance. The MOPT lists three alternates when it shuts: Vara Blanca for light vehicles only, Route 10 between Siquirres and Turrialba, and the Bajos de Chilamate–Vuelta de Kooper corridor.
The Comisión Nacional de Emergencias has moved the Caribbean and Northern Zone in and out of yellow alert repeatedly through August as each wave passed, so check its current declaration before you commit to a trip rather than assuming this week matches last week. The thing to do for anyone near a river, quebrada or low-lying road stays the same as it has all month. Do not cross flooded roads or swollen watercourses, on foot or in a vehicle. Move early if water starts rising near your home rather than waiting to see whether it stops. Call 911 if you need evacuation.
