Tradewinds from the northeast keep Puerto Rico's climate equable, although tropical. San Juan has a normal daily mean temperature of 80°f (27°c), ranging from 77°f (25°c) in January to 82°f (28°c) in July; the normal daily minimum is 73°f (23°c), the maximum 86°f (30°c). The lowest temperature ever recorded on the island is 39°f (4°c), at Aibonito, the highest 103°f (39°c), at San Lorenzo. The recorded temperature in San Juan has never been lower than 60°f (16°c) or higher than 98°f (37°c).
Rainfall varies by region. Ponce, on the south coast, averages only 32 in (81 cm) a year, while the highlands average 108 in (274 cm); the rain forest on El Yunque receives an annual average of 183 in (465 cm). San Juan's average annual rainfall is 54 in (137 cm), the rainiest months being May through November.
The word "hurricane" derives from hurakán, a term the Spanish learned from Puerto Rico's Taino Indians. Nine hurricanes have struck Puerto Rico in this century, the most recent being the devasting Hurricane Georges in 1998. On 7 October 1985, torrential rains created a mud slide that devastated the hillside barrio of Mameyes, killing hundreds of people; not only was this Puerto Rico's worst disaster of the century, but it was the single most destructive landslide in US history.