Harbour Island Bahamas weather is truly magnificent all year round. With the exception of an occasional rain shower in the late afternoon, it’s sunny 340 days out of the year. And, in late winter and spring there is hardly any rainfall at all. The temperature in Dunmore Town averages 74° in the winter, 78° in the spring and fall, and 83° in the summer. With only a 20° difference in temperature from summer to winter there’s no off-season which means it’s never too hot or too cold to visit Harbour Island.