August is the middle of the off-season in Puerto Rico, with temperatures in the mid-80s Fahreneheit throughout much of the island. This time of the year is the peak of hurricane season for the region. Historically, the most rain and the most damaging storms occur in August.
The midday sun sometimes brings the temperature into the 90-degree range during August, but a cool breeze permeates much of the area in the morning and late afternoon. Frommer's describes the climate of Puerto Rico as one of the most consistent and unchanging in the world, as temperatures are expected to be between 75 and 85 F for most of the year.