The trade winds that blow almost continually throughout The Islands of The Bahamas give the islands a warm, agreeable climate that varies little year-round. Winter temperatures range from 60°F at night to about 75°F during the afternoon in Nassau/PI. Temperatures tend to be similar all over The Bahamas, but are usually somewhat lower than Nassau/PI in the northerly islands during winter and about five degrees higher in the southern islands in summer months. The most refreshing time is between September and May, when the temperature averages 70-75°F. The rest of the year is a bit warmer with temperatures averaging between 80-90°F. Sea surface temperatures normally vary between 74°F in February and 83°F in August.
Humidity is fairly high, especially in the summer months. Winds are predominantly easterly throughout the year, but with a tendency to become northeasterly from October to April and southeasterly from May to September. Wind speeds are, on average below 10 knots; in winter months, periods of a day to two of north and northeast winds of about 25 knots may occur.
There are more than seven hours of bright sunshine per day in Nassau/PI on average, though periods of a day or two of cloudy weather can occur at any time of year. The length of day (the interval between sunrise and sunset) varies from 10 hours and 35 minutes in late December to 13 hours and 41 minutes in late June.
Rain showers occur any time of the year, but the rainy months are May to October. In Nassau/PI, rainfall averages two inches a month from November to April and six inches a month from May to October. In the northern islands, it is up to 20% more. The southern islands normally receive only half the Nassau/PI total. Rainfall is mainly in the form of heavy showers or thundershowers, which clear quickly.
This report copied from Bahamas.com