The Climate of Puerto Rico

On June 1st we welcomed the Commonwealth of Puerto Rico to the CoCoRaHS community, expanding the reach of CoCoRaHs from the tropics of the Pacific (Hawaii) to the tropics of the western Atlantic and eastern Caribbean.

Somewhat rectangular in shape, Puerto Rico is the smallest and most eastern of the Greater Antilles Islands. Puerto Rico's mountainous terrain comprises about 60 percent of its 3,425 square miles. Surrounding the mountainous interior, where the largest peak is Cerro La Punta at 4,390 feet, there are coastal lowlands which extend in to the interior 8 to 12 miles in the north and 2 to 8 miles in the south.  Most of the major population centers are located along the coasts, and so it's likely that most of the CoCoRaHS observers will be located along the coasts as well.

If you place an island with significant terrain in a tropical ocean you should expect quite a variation in precipitation across that terrain. Puerto Rico is no exception.  Average annual rainfall ranges from less than 30 inches to more than 170 inches. Within that range, there is a lot of variation with the highest amounts found in the higher elevations and lowest amounts along the southern coast.

There is no "dry" season in Puerto Rico, although February to April tends to be when rainfall is the lowest. During the fall season westerly moving tropical waves bring showers and thunderstorms to the island, and of course it is also hurricane season.  Puerto Rico has had many brushes with tropical cyclones, but the last hurricane to cause major damage to the island was Hurricane Georges in September 1998. In 2011 Tropical Storm Emily produced torrential rains over the island causing flooding and landslides.

The wettest location on the island is Pico Del Este, a mountain peak on the eastern end of Puerto Rico at an elevation of 3,408 feet in the Caribbean National Forest. The average monthly rainfall ranges from 10.27 in March to 18.61 inches in November, with an annual average of 171.06 inches.  The driest location is Magueyes Island, located just a stone's throw off of the southwest coast. Average annual precipitation here is 29.24 inches, ranging from 1.14 inches in March to 4.58 inches in September.

Location of Pico del Estes (left) and Magueyes Island (right)

Temperatures do not vary much from month to month and generally range between 70°F and 90°F. In San Juan, for example, the average maximum is 83.1°F in both January and February, rising to 88.9°F in September.  Lows range from 70.7°F in January 76.8°F in August. In the mountains lows range from the upper 50s to low 60s and highs from the mid 60s to low 70s.  The warmest weather is typically found along the southern coast up and around the east coast to the northeast coast near San Juan.

Temperature means and extremes for San Juan.

Puerto Rico is on Atlantic Standard Time and does not observe Daylight Savings Time.
  
An excellent web site to learn more about Puerto Rico,from its history and culture to geography and economy is Welcome to Puerto Rico!

More information about the climate of Puerto Rico can be found at the Southeast Regional Climate Center website.