Welcome Back to the forum Daltongang!
The short answer for me is that March is a pretty good month for weather, generally sunny nationwide, but definitely not among the hottest months. However, I wouldn't really worry about the heat in April, since the temperature range between the two months isn't going to be major. The long answer follows...
The weather in Costa Rica is completely dependent on what part of the country you are talking about visiting. The country is of course very small, so people tend to talk about a December to April "summer", which is typically the "dry" season. May to November is called the "rainy" or "green" season.
To me, this is all a little misleading. The volcanic peaks and mountain ranges contribute to the creation of microclimates, so you can go from sunny and hot to fresh and cool within 15 minutes! I live in Coronado, which is in the mountains to the east of San José and our hottest and driest month is March. However, anyone living on the beach would probably ridicule me for calling March in Coronado hot.
In addition to the altitude and microclimates, you have to take into account the transitions between seasons and the cold or warm fronts that tend to sweep down from the north. For example, December and May are transition months, so you can get either summer weather or rainy season weather. And in my part of the country, the coldest months are December and January, but mainly when a real cold snap is going on in the U.S., since at other times we can have really nice weather in those months. Another example is July and August, which are in the middle of the rainy season. However, late June and early July traditionally have a couple of weeks of "veranillo", which means little summer. This occurs mostly in teh Central Valley, Guanacaste and the Central Pacific areas and it meanst that temperatures rise and it gets drier than the following or preceding months.
So I'm sure that all confused you a lot more than it helps, but it just goes to show that it's pretty hard to generalize the weather in Costa Rica and even harder to plan your vacation around it!
Thanks again for posting and come back soon!
