One of the nice things about Costa Rica, is that if you are in an area where it rains too much, you can be in a dry area in a matter of a couple hours. A perfect example of this is the province of Guanacaste which is a tropical dry forest. This means that during the dry season it's even dryer. So during the rainy season, you'll have a rain shower every 2 weeks that will be enough to turn everything green. In the wet, humid and montane forests, rain will be much more present. It may rain for a week straight and then stop for a week or you may get 2 days of rain, 3 of sunshine and 2 more of rain.
The central valley area (San Jose) has a great balance where it will rain normally during the late afternoon or evening while the day will offer beautifull sunshine. Every so often San Jose will get showered for a few days.
Since the country is so small (about the size of West Virginia), you can move about the country to where the climate is to your liking. So when planning your trip you would want to pack for two climates. This will allow you to get soaked on account of the rain, but you'll always have a set of dry clothes with you. Most places will have changing rooms.
Some may think that the rain will hinder the activities but it may make them more entertaining. Specially if the rain comes and goes in light and heavy showers. This may seem odd but it's a mix that really brings the forest to life. Animals will move when the rain stops and hide when it returns. Flowers release their scent and if the sun is out while it rains, when it stop everything shines bright. You suddenly forget about the urban jungle and allow the forest to suck out all negative energy and stress.
Next week we'll discuss ideal exploration routes through Costa Rica.