When is the best time to visit Costa Rica for Arenal?

Costa Rica is not one climate but two slopes divided by a cordillera, and Arenal sits on the wetter of them. Nationally the dry months run December through April; the Pacific coast dries out hardest, the Caribbean side least, and the volcanic spine in between holds cloud for much of the year. That is the single most important thing to understand about timing a trip around Arenal: the national dry season improves your odds of a clear summit, it does not guarantee one, and the odds are best in the first hours after the park's 8:00 opening.

Scale the trip to the country, not to the volcano. Within a few hours' drive of Arenal, the Monteverde Cloud Forest Biological Reserve keeps entirely different hours — 7:00 to 16:00, every day of the year including holidays — and sits in a different forest type altogether, so a single itinerary can pair a dry-season volcano with a cloud forest that is never dry. Costa Rica's four UNESCO World Heritage properties lie further out still: Cocos Island National Park in the Pacific, Área de Conservación Guanacaste in the northwest, the Talamanca Range-La Amistad Reserves with La Amistad National Park on the Panamanian border, and the Precolumbian Chiefdom Settlements with Stone Spheres of the Diquís in the south.

Arenal itself needs its record set straight before dates are chosen. The Smithsonian Institution's Global Volcanism Program gives the summit as 1,670 meters (5,479 feet) and records that the eruption which began on the night of 29 July 1968 declined after September 2010, with the last sporadic Strombolian explosions in December 2010. The Costa Rica Tourism Board puts the national park's altitude range at 500 to 1,633 meters, and lists the Las Coladas trail at 1.7 kilometers one way with 20 minutes allowed at the lava viewpoint. The lava is there; the eruption is not.

In February the Pacific lowlands go brown and the wind off the Nicoya side is dry and constant, while the ground around Arenal stays green — the cordillera wrings the moisture out before it reaches the other coast. On a clear dry-season morning the cone is sharply drawn against the sky by seven and softening behind cloud by eleven.

Entry is cashless and documented. The tourism board's park sheet for Arenal Volcano National Park states that tickets are bought at the entrance by credit or debit card only, with no cash accepted, and that entry requires a passport or identity document — a combination that catches travelers arriving straight off a domestic flight. Nationally, the entry rules are generous but conditional: US citizens need no visa for stays under 180 days but must hold a return ticket, a passport must be valid for the period of the stay, and a yellow fever vaccination certificate is required of travelers arriving from certain countries in South America or Africa.

• February and March — The driest stretch nationally, and the best chance of the cone and the Pacific coast both behaving on one trip.
• April — Still dry, with the first build of humidity on the Caribbean slope; good for Arenal, hot on the Pacific.
• May to November — The wet months. Mornings still open clear on the volcano more often than afternoons do.

Crime is the subject of the State Department's standing advice on the country, which tells travelers to exercise increased caution. Leaving by air carries a US$29 departure tax, usually included in the fare, and British passport holders need an expiry date at least one day after the day they plan to leave. Arenal's gates shut at 16:00 year-round, so no season gives you the park at dusk. Driving between Arenal, Monteverde and either coast is slow mountain road rather than highway, and the dry season does not change that.

The places-and-experiences answer in this group covers the four World Heritage properties and the private reserves; the trip-planning answer sets out entry rules, taxes and a realistic two-week shape.