The most readable charts of this entire area are those developed by Street and published by Imray-Iolaire in Great Britain. They are available from some US chart supply houses. The Caribbean is a fantastic cruising ground throughout the year. Temperatures don't vary more than a few degrees all year round. The Trade Winds blow most of the year, strongest and most reliable during the winter months.
Rain showers occur throughout the year, but more frequently during the summer months.
During the summer months there is a danger of hurricanes. However, in the southern part hurricanes are rare. The southern Grenadines and Grenada have only been hit a couple of times in the last twenty years. Many cruising sailors return to the United States during these months, others go further south to Grenada and Venezuela and the Dutch Antilles, south of the hurricane zone. The increase in numbers since I first visited these islands in 1987 has been dramatic.