Costa Rica's dry season: how it works, month by month

What Costa Ricans call summer is, for the National Meteorological Institute (IMN), the dry season. Here is how it works, when it reaches each region and how much rain falls month by month, according to official records.

How the dry season works, step by step

The IMN defines the seasons with a rainfall threshold: there is a dry season where at least three months in a row average 80 millimetres or less, and a rainy season where they exceed it. To divide the country into regions it used data from 727 stations between 1960 and 2013, and to set the start and end dates, daily rainfall from 1991 to 2020.

1. 1
   November, the transition. In the Central Valley and the North Pacific the rains start to ease: it is a bridge month into the dry season.
2. 2
   December, it begins. The intertropical convergence zone, the band of clouds that brings the rains, moves south and loses its grip on the country.
3. 3
   December to February, the cold surges. Dry, stable air masses arrive from the north and limit rainfall even more, above all on the Pacific side of the volcanic range.
4. 4
   March, the close. It is the last month of the dry season in the North Pacific and the Central Valley; in Liberia it averages 4.9 millimetres and a single rain day.
5. 5
   April, the transition. The first rains return: Liberia gets 46.5 millimetres over 4 days on average, and Juan Santamaría airport 126.3 millimetres over 11 days.
6. 6
   May, the rain returns. In the Central Valley the rainy season usually starts in the second half of May.

Timeline

How much rain falls in the dry season, in figures

Liberia gets 1,545.9 millimetres a year on average, spread over 132 rain days; January, February and March together add up to just 6.5 millimetres, less than 1 % of the total. At Juan Santamaría airport the annual average is 1,936.4 millimetres over 182 rain days, and the dry season is wetter too: December there totals 32.8 millimetres, almost three times Liberia's.

Curious facts

• According to the IMN, the North Pacific is Costa Rica's most arid region, and much of it lies within the Central American Dry Corridor.
• In Liberia, February holds both the highest (39.7 °C) and the lowest (15.1 °C) temperatures recorded at the airport between 2005 and 2025.
• The Western Valley gets more rain than the Eastern (2,300 against 1,700 millimetres a year), but the Eastern has more rain days (163 against 148), because of the Caribbean's influence in December, January and February.
• The rainy season has its breaks too: the short “veranillo de San Juan” arrives in late June, and between July and August comes the canícula or veranillo.

Frequently asked questions

Is the dry season a public holiday in Costa Rica?

No. It is a climate season. It is not among the public holidays of article 148 of the Labour Code, according to the Ministry of Labour's official 2026 calendar.

When does the dry season start?

It depends on the region and the year. For 2026, the IMN forecast the start between 3 and 15 November in the North Pacific, between 8 and 23 November in the Central Valley, between 13 and 30 November in the Central Pacific and between 30 November and 3 December in the South Pacific. They are that year's forecasts, not fixed dates.

Why does it rain in the Caribbean during the dry season?

Because that side of the country has no dry season: according to the IMN, the northern Caribbean, the southern Caribbean and the eastern northern zone record rain all year round.

Sources

• IMN: estimated start and end dates of the rainy season by climate region, 1991-2020 (Climatology Unit, 2022).
• IMN: 2005-2025 aeronautical climatology of Daniel Oduber international airport (Liberia).
• IMN: 2005-2023 aeronautical climatology of Juan Santamaría international airport (table 1, 2010-2022).
• IMN: Central Region, Central Valley climate (1961-1990).
• La Nación: “IMN announces when the dry season will begin” (20 October 2026).
• Delfino: “IMN recognised as a Meritorious Institution” (10 April 2025).
• Ministry of Labour and Social Security: 2026 holiday calendar (4 December 2025).