Two rainy seasons, not one
What the media and most guidebooks call “Panama’s rainy season” is really the Pacific-side invierno, the wet half of the year that runs from roughly May to November on the south coast. The Caribbean side has a different rhythm: rain year-round, with a relative lull from February through April. The asymmetry is driven by the cordillera: the trade winds drop their moisture on the windward (Caribbean) slopes, leaving the Pacific lowlands in seasonal rain shadow during the months when the Inter-Tropical Convergence Zone sits south of the country.
The Smithsonian Tropical Research Institute’s national stations layer (ETESA + ACP + STRI) is the canonical reference for current conditions[2], and the country’s rainfall regime is modulated year-to-year by the El Niño–Southern Oscillation, which NOAA’s Climate Prediction Center tracks via the Oceanic Niño Index (ONI): a 3-month running mean of ERSST.v5 SST anomalies in the Niño 3.4 region, with El Niño declared above +0.5 °C and La Niña below −0.5 °C for at least five consecutive overlapping seasons[1].
The Pacific-side calendar (Panama City, Azuero, Pacific Chiriquí)
January
The driest month of the year on the Pacific side. Rainfall at Panama City typically totals 25–40 mm[2]; the Arco Seco stations can record their annual minimum this month. Mornings are clear and breezy; afternoons occasionally build a brief convective shower that passes quickly. The trade winds are at their weakest, so the air feels calm.
This is peak tourist season: clear weather, low humidity, comfortable temperatures, no tropical-wave rain to disrupt outdoor plans. The Pacific-side highlands (Boquete, El Valle) are also at their driest and most pleasant, though night-time temperatures can dip into the low teens in the highest valleys.
February
Much like January but with a slow uptick in humidity. Rainfall totals remain low (40–60 mm at Panama City)[2], and the dry-season pattern holds. The nortes (cool northerly winds) can bring overnight lows into the low 20s on the Pacific lowlands and down to 10–12 °C in the Chiriquí highlands. Carnaval falls in February or March, depending on the liturgical calendar, and the dry-season weather is part of why the Las Tablas and Penonomé celebrations draw large crowds.
March
The last full month of the dry season. Rainfall begins to creep up (60–100 mm at Panama City)[2], and the first convective thunderstorms of the year can pop up in the afternoons. The Arco Seco’s annual minimum is typically in March. Holy Week processions and inland tourism are concentrated in March–April, with dry-season weather mostly intact.
April
The transition month. The Inter-Tropical Convergence Zone is migrating northward, and Pacific-side rainfall ramps up sharply: Panama City typically records 80–150 mm in April[2], with most of it in the second half of the month. The first multi-day rainy spells can occur in late April, and outdoor plans become more weather-dependent. The first tropical waves of the Eastern Pacific season can begin to form by late April, though they typically track west-northwest and don’t affect Panama directly.
May
The invierno is starting. Pacific-side rainfall jumps to 200–300 mm at Panama City[2], with the heaviest events in the late afternoon and evening. Mornings are often clear and humid; the clouds build through the day. This is the most reliable month for the bajareque (the heavy-mist, light-rain pattern that soaks the western cordillera and the Chiriquí highlands).
June
The rainy season is in full swing. Pacific-side rainfall is typically 250–350 mm[2]. The Pacific-side veranillo, a brief mid-summer dry interlude, sometimes arrives in late June, occasionally earlier. The Eastern Pacific hurricane season is open, though most storms track west-northwest and don’t threaten Panama.
July
This is the veranillo month in years that have a clear one. Rainfall at Panama City can drop to 100–200 mm in a[2] veranillo year, mostly in afternoon showers; in years without a strong veranillo, July rainfall runs 200–300 mm and the rainy pattern continues. The coffee harvest in Boquete and the sugar harvest in the Arco Seco both depend on the veranillo for ripening and cutting windows.
August
The veranillo usually fades by early August, and the full invierno resumes. Rainfall is 250–350 mm at Panama City[2], with high humidity and frequent tropical-wave passages. The Atlantic hurricane season is at its climatological peak, though Panama’s low latitude still places most storms to the north.
September
The climatological peak of the Pacific-side invierno. Rainfall is 250–400 mm at Panama City[2], with frequent heavy multi-day events and high river levels on the Río Chepo, Río Chagres, and the lower Río Santa María. The first significant Atlantic-basin tropical-storm peripheral rainfall can affect the Caribbean coast this month, even without a direct impact.
October
The second peak of the invierno, often tied to the seasonal migration of the ITCZ southward and the most-active Atlantic hurricane period. Pacific-side rainfall remains 250–350 mm[2]; Caribbean-side rainfall is at its annual maximum. Tropical-storm peripheral rainfall on the Caribbean coast is most likely in October. The Panama Canal’s freshwater management is most stressed this month.
November
The invierno tapers off through November. Rainfall drops from 200 mm early[2] in the month to 100–150 mm late, and the first multi-day clear spells return. The second half of November is the most reliable “shoulder season” (dry enough for outdoor plans on the Pacific side, fewer tourists than December through March).
December
The dry season returns. By mid-December most of the Pacific lowlands are back to their dry-season pattern, with occasional early dry-season showers and clear, breezy weather. Christmas and New Year are dry-season-peak tourist events; Panama City’s average December rainfall is 60–100 mm[2].
The Caribbean-side calendar (Bocas del Toro, Colón, Guna Yala)
The Caribbean coast is rain year-round. The relative lull comes in February through April, when monthly totals drop to 100–200 mm (low for a perhumid tropical coast) and the trade winds are steady. From May through December, monthly totals run 300–600 mm at most stations, with peaks in October–December tied to trade-wind surges and tropical-wave passages.
The practical implication: there is no “dry season” on the Caribbean side, only a relatively less wet window in February through April. Travel and outdoor work on the Caribbean coast are weather-dependent year-round, but the December–March window is the easiest, especially for trips to Bocas del Toro, the San Blas archipelago, and the upper Chagres basin.
The highland calendar (Boquete, Volcán, Cerro Punta)
The Chiriquí highlands run on a slightly compressed version of the Pacific-side calendar, with a few local twists:
- The dry season is shorter (January through March, sometimes into early April) but also less extreme, because the cordillera’s height forces orographic precipitation year-round.
- The bajareque (the heavy-mist, light-rain pattern) is most pronounced in May through August and is essential to the highland coffee and vegetable crops.
- The veranillo is the critical ripening window for the coffee harvest (October through January). A weak veranillo delays the harvest and degrades quality.
- Overnight lows can drop to 10–12 °C in the dry season and 5–8 °C in the highest valleys, especially under clear skies with active nortes.
ENSO modulation
The calendar above is the long-term mean. Year-to-year, ENSO shifts it by weeks:
- El Niño years. The Pacific-side invierno tends to start late, run drier, and end early. The dry season effectively extends. Caribbean-side effects are weaker.
- La Niña years. The invierno starts early, runs wetter, and can extend into December. Caribbean-side tropical-wave activity is enhanced.
- Neutral years. Close to the long-term mean.
The strongest recent reference was the 2023–2024 El Niño, which peaked at ONI +2.1 in December 2023 (one of the strongest on record) and contributed to drier-than-average Pacific-side conditions and Canal-watershed stress into 2024[1]. The 2025 weak La Niña (ONI −0.1 to −0.6) brought a closer-to-average invierno but with a sharper Caribbean-side wet season.
How to use this calendar
For travel planning, the practical rule of thumb is:
- Pacific-side beach and outdoor travel. December through April. The dry-season guarantees don’t extend past late April; the second half of November is a useful shoulder.
- Caribbean-side travel. February through April is the driest; May through November requires flexibility for tropical-wave rain. December–March is also pleasant but slightly wetter than the dry-season peak.
- Highland and coffee-country travel. December through March for the dry-season feel; May through August for the bajareque and the green-season look (preferred by photographers).
- Carnaval. February or March (varies by year). Best to plan around, not against.
- Surf and wind sports. The Pacific-side invierno brings the most consistent southern-hemisphere swell, peaking in June through September. The Caribbean side has trade-wind-driven conditions year-round, with peaks in February through April.
For agricultural planning, the ENSO outlook from NOAA CPC is worth tracking at least two seasons ahead. Strong El Niño years can compress the dry season and stress the Canal watershed, while strong La Niña years can produce extended flooding on the Río Chepo, Río Santa María, and Río Chucunaque.
When to skip and when to read on
If you’re picking dates for a trip, the one-line answer is: December through April for the Pacific side; February through April for the Caribbean side; check the NOAA CPC ENSO outlook for year-to-year shifts. The climate-of-panama page covers the underlying physics; the climate-by-region page breaks the calendar down by region; and the best-time-to-visit page in the travel section distils the calendar for trip planning.
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