February to April is the driest and most reliable window on the Pacific side and in the Central Valley. May and November are the shoulder months that keep most of the good weather at a fraction of the price.
The complication worth knowing before booking anything: Costa Rica runs two weather calendars, and they are roughly opposed.
The two seasons, on the Pacific side
| Months | What it is | |
|---|---|---|
| Dry ("summer") | Dec–Apr | Sunny, hot, dusty in the north-west. Peak prices and crowds. |
| Green ("winter") | May–Nov | Mornings clear, afternoon downpours. Everything is green. |
The green season is not a washout. The typical pattern is clear mornings, rain in the afternoon for one to three hours, then clearing. Mornings are usable almost every day, which is why a tour operator's day trips still run.
September and October are the exception — the wettest part of the year on the Pacific, with rain that can last all day. Several Pacific operators close.
The Caribbean side is on a different calendar
Puerto Viejo, Cahuita and Tortuguero do not follow the Pacific pattern at all.
| Caribbean coast | |
|---|---|
| Driest | September and October |
| Also good | February and March |
| Wettest | November to January |
This is the single most useful fact about timing a Costa Rica trip. September and October — the worst months on the Pacific — are the best on the Caribbean. A trip in those months should be planned around the Caribbean coast, and it will be quiet and inexpensive.
Planning a September trip around Manuel Antonio and Guanacaste is choosing the wettest weeks of the year in the wettest place.
Month by month
| Month | Pacific | Crowds & price |
|---|---|---|
| December | Dry, warm | Very high from mid-month |
| January | Dry, breezy | High |
| February | Driest | High |
| March | Dry, hot | High |
| April | Dry, hottest; rain returns late | High to Easter, then falls |
| May | Green season begins, afternoon showers | Low — good value |
| June | Afternoon rain, green | Low |
| July | "Veranillo" — a drier spell mid-month | Moderate |
| August | Afternoon rain | Moderate |
| September | Wettest | Lowest |
| October | Wettest | Lowest |
| November | Rain easing, everything green | Low — good value |
| December | Dry again | Rising fast |
May and November are the value months. May still has most of the dry-season feel in its first half; November has the landscape at its greenest with the rain tailing off, and prices have not yet turned over for the December peak.
Booking around the peaks
Christmas to New Year and Easter week are the two genuine peaks. Domestic travel adds to international demand, prices roughly double, and popular lodges fill six months to a year ahead.
Outside those two windows, the dry season is busy but bookable a month or two out. The green season is bookable almost on arrival.
What the month decides beyond weather
Turtle nesting on the Caribbean at Tortuguero runs roughly July to October — which is the Pacific's wet season and the Caribbean's dry one, so the calendars work in your favour.
Whale watching has two seasons on the Pacific, from northern and southern hemisphere populations, with a long window around July to October.
Surf is better on the Pacific during the green season, when the swell is larger. Green season is high season for surfers, which is the one group for whom the pricing runs backwards.
Roads. Green season turns unpaved access roads to remote lodges into a four-wheel-drive question. Ask the lodge, not the rental company.
Getting there is its own arithmetic: flight times are governed by wind rather than distance, and Costa Rica sits on Central Standard Time with no daylight saving, which changes the offset from home twice a year.