The weather in Costa Rica in December is dry for much of the country, remaining so until April.
December is high season along the Pacific Coast, Monteverde and the interior of Costa Rica.
The Caribbean Coast however experiences some rain in December until things clear up generally in February.
Snorkelling conditions are generally good on the Pacific Coast at this time of year, off the Corcovado National Park, where dolphin watching is also possible throughout the year.
Being close to the equator, Costa Rica enjoys 12 hours of daylight throughout the year, with sun rising and setting just before 6 am and 6 pm.