Nicaragua is great to visit all year round. The rainy season runs from mid May to late November. Some tourists actually prefer to come over the rainy season because the country is beautifully green and not too hot. The rain usually falls at the end of the day for one hour or two.
The dry season is from December to mid May and in this period it is very hot and dry. The end of the dry season is the best time to snorkel in off the Caribbean coast; the water is calm and the visibility perfect.