I'd rephrase that to June or July; if you leave during August you risk missing a nice hurricane swell. That's if you plan on going to Central America. If you plan on going to the Caribbean and one of those things hits, prepare to get your balls out of your throat when the wave is over because they will most likely be dislodged on the drop. That is if they are not made of steel.
Actually, Costa Rica has two seasons, summer (verano) and winter (invierno). And they are reversed relative to the US even though CR is not in the Southern Hemisphere. Verano is the dry season and runs roughly from December through April while invierno is the rainy season and runs from May through November. If you plan on going to CR during our (US) summer it will be their 'winter' (rainy season) and you'll want to head to the Central and South Pacific Coast not the Caribbean or Nicoya Peninsula.
from what i understand..... dry and wet seasons (the monsoons) are not the same things as our summer-fall-winter-spring seasons. Summer in simply a calendar event that corresponds to a particular astronomical position of the sun in the northern hemisphere, i.e. beginning on the summer solstice June 21st. On the other hand, the monsoon is a seasonal shift in trade winds as well as atmospheric circulation. In other words one is an astronomical event while the other is a meteorological effect that is eventually the end result.
While the rainy season may indeed be called the 'winter monsoon' it is simply a misnomer. It is still summer this time of year above the equator.
Does that sound correct? There were some confusing sounding posts here...