Best Time of Year to Travel
In Costa Rica, the tourist season has traditionally been from December 15 through April 15, which corresponds to the dry season. You can almost depend on clear, sunny weather, but there are occasional unseasonal storms from the north that can last for several days.
The rainy season usually takes a while to get started in April, and often diminishes for a couple of weeks in June or July. The rains dwindle in December. In Guanacaste, the only really rainy months are October and November. On the Atlantic side, the only predictably dry months are September and October, but it is often sunny there during the traditional January to April dry season.
Now that Costa Rica has become so popular, July and August are also considered the high season, and popular hotels charge high-season rates despite the rain.
There are certain advantages to going during the Costa Rican "green" season: The mornings are almost always clear and warm. The scenery is fresher and greener. The days are cooled by the rains, which can be a blessing, especially at the beach. The clouds usually clear in time for a magnificent sunset.
Many hotels now consider May 1 to June 15 and September 1 to November 15 to be the off-season, and offer substantial discounts.
You really need to plan ahead for Christmas week and the week before Easter. Hotel rooms are booked six to ten months in advance, and popular hotels are often booked several months in advance during the January to April dry season as well.
If you want to try less frequented beaches, like Zancudo in the Southern Zone or the beautiful beaches of Talamanca on the Atlantic, you can take a "let's just explore and see what happens" vacation, and you'll almost always find a place to stay. But hotels that have gotten good reviews on Trip Advisor will usually be booked up.
Airlines are usually booked far in advance from about December 10 to January 10, so make your plane reservations early if you want to go during that time. The same goes for the weeks before and after Easter.