The cloud forests, such as Monteverde and Saint Elena, and the rest of Costa Rica’s national parks, including Manuel Antonio, Corcovado and Tortuguero, have a very high rainfall. In the cloud forests and around Arenal Volcano, the average is 444mm for the month, then in Corcovado and on the Osa Peninsula, the average for the month is 722mm. This makes the terrain muddy and often tough to navigate and occasionally the roads are not passable due to landslides or higher river crossings. Wildlife at this time will hide from the heavy rains, making them difficult to spot. Rain still falls in intervals, but the rainfall bursts to tend to be longer in September, with less chance of sunshine to break it up.
Down in the southern part of the Pacific Coast, humpbacks are still gathered in the Marino Ballena National Park in Dominical, so whale watching is available.
Over on the Caribbean Coast, rainfall is less, averaging at 250mm for the month, and the temperature reaches about 30 degrees Celsius. A safari in Tortuguero National Park may be possible, and it is still nesting season for the green sea turtles, where you may be able to see them making their way to the sea for the very first time.
If you are hoping for some beach time, you are best off heading to the northern Pacific Coast which receives less rain throughout the year, but we cannot guarantee bright sunshine at this time.