Costa Rica Weather

17/09/2026

9:57 am September 17, 2026 El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter of 2026-27. The CPC& #39;s official ENSO outlook, which synthesizes multiple North American and international models, indicates that El Niño will continue to strengthen through the end of the year (Figs. 6-8). During the October-December 2026 season, there is a 75% chance of a historic event that would exceed the intensity of previous El Niño events in the record dating back to 1950 (+2.5°C or more for a 3-month RONI value). With an event of this magnitude, the likelihood of experiencing El Niño-consistent impacts is higher, but not guaranteed (refer to the CPC outlook for seasonal anomaly probabilities). In summary, El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter of 2026-27. -- This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), the NOAA National Weather Service, and their funded institutions. Ocean and atmospheric conditions are updated weekly on the Climate Prediction Center website (Current El Niño/La Niña Conditions and Expert Discussion). -- Source: NOAA-10-09-2026

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17/09/2026

Advisory: Afternoon showers and movement of Tropical Wave #44. Issued: September 17, 2026 at 9:20 am. More details: https://www.imn.ac.cr/web/imn/avisos-meteorologicos

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Meteorológico: Aguaceros vespertinos y desplazamiento de la onda tropical #44.
Emitido: 17 de septiembre de 2026 a las 9:20 a.m.
Más detalle: https://www.imn.ac.cr/web/imn/avisos-meteorologicos

17/09/2026

9:14 am September 17, 2026 Monthly summary of the status of El Niño, La Niña, and the Southern Oscillation, or ENSO, based on the NINO3.4 index (120-170°W, 5°S-5°N). The 2026 El Niño phenomenon continues to intensify in the central-eastern equatorial Pacific. The traditional Niño 3.4 index shows a clear and sustained increase, with a most recent seasonal average of +1.51°C between May and July 2026 and a monthly increase of +2.03°C in July. The latest weekly Niño 3.4 index, dated August 12, 2026, reached +2.7°C. Taken together, these observations indicate that El Niño is strengthening and evolving into a very strong event. Figures 1 (the official CPC ENSO probability forecast) and 3 (the CCSR/IRI model-based target ENSO probability forecast) are usually quite similar. However, they can occasionally differ markedly. There may be several possible reasons for the differences. One is that human forecasters, using their experience and judgment, may disagree to some extent with the models, which may have known biases. Another reason is that the models are not run at the same time the forecasters make their assessment, so the initial ENSO conditions may be slightly different between the two times. The charts on this Quick View page are updated at two different times of the month, usually about a week apart, and the CCSR/IRI forecast is run later. Note also that the CPC forecast starts in the previous season, while the CCSR/IRI forecast starts in the current season. -- Source: IRI-19-08-2026

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9:14 am 17 de septiembre 2026

Resumen mensual del estado de El Niño, La Niña y la Oscilación del Sur, o ENOS, basado en el índice NINO3.4 (120-170°O, 5°S-5°N).

El fenómeno de El Niño de 2026 continúa intensificándose en el Pacífico ecuatorial centro-oriental. El índice tradicional Niño 3.4 muestra un aumento claro y sostenido, con una media estacional más reciente de +1,51 °C entre mayo y julio de 2026 y un incremento mensual de +2,03 °C en julio. El último índice semanal Niño 3.4, con fecha del 12 de agosto de 2026, alcanzó los +2,7 °C. En conjunto, estas observaciones indican que El Niño se está fortaleciendo y evolucionando hacia un fenómeno muy intenso.
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Las figuras 1 ((el pronóstico oficial de probabilidad ENOS del CPC) y 3 (el pronóstico objetivo de probabilidad ENOS basado en el modelo CCSR/IRI) suelen ser bastante similares. Sin embargo, ocasionalmente pueden diferir notablemente. Puede haber varias razones posibles para las diferencias. Una es que los pronosticadores humanos, utilizando su experiencia y juicio, pueden discrepar en cierta medida con los modelos, que pueden tener sesgos conocidos. Otra razón es que los modelos no se ejecutan al mismo tiempo que los pronosticadores hacen su evaluación, por lo que las condiciones iniciales de ENOS pueden ser ligeramente diferentes entre los dos momentos. Los gráficos en esta página de Vista Rápida se actualizan en dos momentos diferentes del mes, generalmente con una diferencia de aproximadamente una semana, y el pronóstico CCSR/IRI se ejecuta más tarde. Tenga en cuenta también que el pronóstico del CPC comienza en la temporada anterior, mientras que el pronóstico CCSR/IRI comienza en la temporada actual.
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Fuente: IRI-19-08-2026

17/09/2026

Thursday morning (7:20 am). The country is generally experiencing mostly sunny skies, with low clouds along the northern border and a chance of occasional rain. Ultraviolet Radiation Index map for today, Thursday, September 17, 2026.

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inicio de jueves (7:20 a.m.). En general el país amanece mayormente soleado, con nubes baja en la frontera norte del territorio nacional, con probabilidad de lluvia ocasional.

Mapa del índice de radiación ultravioleta de hoy jueves 17 -09 - 2026.

17/09/2026

6:59 am September 17, 2026 Tropical Weather Outlook for the Eastern and Central North Pacific east of 180 degrees longitude. Western Eastern Pacific: A tropical wave continues to produce disorganized showers and thunderstorms well south-southwest of the southern tip of the Baja California Peninsula. Environmental conditions appear favorable for gradual development of this system, and a depression is likely to form this weekend or early next week as it moves westward at 10 to 15 mph across the western portion of the Eastern Pacific. * 48-hour formation chance...low...20 percent. * 7-day formation chance...high...70 percent. -- Well east-southeast of the Hawaiian Islands (former TD15-E): Showers and thunderstorms have increased slightly with an area of low pressure associated with the remnants of Tropical Depression Fifteen-E. Environmental conditions appear only marginally favorable for some development of this system as it gradually moves westward, remaining east-southeast of the Hawaiian Islands. * 48-hour formation chance...low...10 percent. * 7-day formation chance...low...10 percent. -- Southwest of southwestern Mexico: Another tropical wave is producing disorganized showers and thunderstorms several hundred miles south of southwestern Mexico. Environmental conditions also appear favorable for gradual development of this system, and a tropical depression is likely to form late this weekend or early next week as it gradually moves northwestward, turning northward off the coast of southwestern Mexico. * Probability of formation in 48 hours...low...close to 0 percent. * Probability of formation in 7 days...high...80 percent. -- Source: National Hurricane Center (NHC). -- Pay attention to publications from meteorological centers in your country.

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17/09/2026

09/16/26 (6:10 pm) As night begins, cloudy conditions prevail across the country. Scattered showers are reported in the central and southern regions. Meanwhile, convective cells are developing in the Caribbean maritime region.

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16/09/2026

09/16/26 (3:00 pm) This afternoon, abundant cloud cover is observed over much of the national territory, with the exception of areas in the North Pacific, where there is little cloud cover. This condition favors the occurrence of downpours accompanied by thunderstorms in areas of the Central and South Pacific and west of the Central Valley.

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16/09/2026

12:08 pm A slight decrease in humidity is expected across the country this Wednesday, favoring more isolated showers. Tropical waves #44, currently weak and with possible entry into the country on Friday, and #45 are observed in the Caribbean Sea.

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16/09/2026

10:40 am September 16, 2026 Storms and convective cells are observed in maritime areas. Scattered cloudiness is present in regions of the Caribbean and Northern Zone, with drizzle and light rain in some areas. In the rest of the national territory, mostly clear conditions prevail.

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10:40 a.m 16 de septiembre 2026

Se observan tormentas y núcleos convectivos en zonas marítimas. Se presenta nubosidad dispersa en regiones del Caribe y Zona Norte, con lloviznas y lluvias débiles en algunos puntos. En el resto del territorio nacional, predominan condiciones de poca nubosidad. Según.IMN-26-09-2026 hoy miércoles se espera una leve disminución en la humedad sobre el país, lo cual permitirá que las lluvias sean más aisladas, sin embargo, los vientos alisios moderados estarían presentes en el mar Caribe, con posibilidad de chubascos ocasionales para esta vertiente. Por la mañana, habrá lluvias y chubascos dispersos en el Caribe y la Zona Norte, mientras el resto del país disfrutará de nubosidad de poca a parcial. Hacia la tarde, disminuyen las precipitaciones en Limón y norte del país para dar paso a algunos aguaceros aislados con tormenta en la vertiente del Pacífico y de manera dispersa en la Gran Área Metropolitana (GAM).

15/09/2026

3:10 pm 09/15/26 At this time, the country remains mostly cloudy. We have reports of drizzle and light rain in the North Caribbean and Northern Zone; some of this activity is moving to the Central Valley and Pacific Slope.

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3.10 p.m. 15.09.26 A esta hora el país se mantiene muy nublado en su mayoría. Tenemos registros de lloviznas y lluvias débiles en el Caribe Norte y Zona Norte, parte de esta actividad se traslada al Valle Central y Vertiente del Pacífico.