Climate of Puerto Rico
The climate of Puerto Rico in the Köppen climate classification is predominately tropical rainforest. Temperatures throughout the year are warm to hot, averaging near in lower elevations and in the mountains. Easterly trade winds pass across the island year round while the rainy season stretches from April into November. The relatively cool trade winds are blocked by the mountains of the Cordillera Central which causes rain shadows and sharp variations in the temperature and wind speed over short distances. About a quarter of the average annual rainfall for Puerto Rico occurs during tropical cyclones, which are  more frequent during La Niña years. Temperature. Temperatures range from in the lower elevations, while higher elevations in the central part of the island experience temperatures between year round. The temperature in the south is a few degrees higher than the north. Between winter and summer, there is only a temperature swing of around . Coastal water temperatures average between 77 °F in February to 87 °F in August. The highest temperature ever recorded was at San Lorenzo, while the lowest temperature ever recorded was at Aibonito. Dust from the Sahara. For years, meteorologists have been studying dust that  arrives from the Sahara Desert, and they believe the dust which is carried over the Atlantic to Puerto Rico causes a whole series of changes in Puerto Rico's climate and environment, from haze to heat. Wind. Persistent trade winds move from east to west across the island year round. When the trades winds are lighter, sea breeze and land breeze circulations dominate. Every five years or so a hurricane brings high intensity wind. The island's infrastructure is extremely susceptible to high winds. For example, when Hurricane Maria made landfall on the island in 2017 at Category 5 strength , 100% of the power grid was lost. Rainfall. There is a pronounced rainy season from April to November and a dry season from December to March, causing some drought. Due to the island's topography, rainfall varies greatly across the island. Pico del Este averages of rainfall yearly while Magueyes Island averages only a year. Severe weather. Approximately 80 percent of the territory's agriculture was lost due to the hurricane, with agricultural losses estimated at $780 million. The hurricane completely destroyed the island's power grid, leaving all 3.4 million residents without electricity. Hurricane Maria caused a humanitarian  crisis in Puerto Rico, with damages estimated in 90 billion dollars and a loss of human life close to three thousand. Weather by season. The Wet Season begins in April and lasts to November. The weather is hot and humid with thunderstorms in the afternoon, especially in August and September. Trade winds bring cool summer breezes in the north and east of Puerto Rico, but due to the topography of the island, these winds do not reach the coast south and west, causing much higher temperatures than in the north. During humid summer days, the heat index can reach 115  °F (47 °C) and actual temperatures can reach 100 °F (38 °C). Sometimes the wind shifts from the south, causing an inverse pattern, where the heat south of the island moves to the north, causing temperatures in the mid 90s (35 °C) in San Juan and low humidity. June is usually the driest month of the summer. During June and July the precipitation is mostly caused by the effects of humidity and heat of the island. The peak of the hurricane season comes in September. Weather conditions can be very rainy as tropical lows pass  near the island, with frequent strong thunderstorms. By early November the tropical cyclone season fades and the weather becomes drier and generally sunny. December brings the Dry Season which lasts through March. Weakening cool fronts from the north lower temperatures and humidity, and dry and sunny conditions prevail. In San Juan in the winter months, high temperatures reach 77–87 °F (25–30 °C) with an average high of 83 °F and lows down to 66–76 °F (19–24 °C), giving an average of 71 °F (22 °C). In the central area of the island the  elevation and reduced sea effects bring the minimum temperatures to 55–65 °F (13–18 °C) on average. After fronts pass the temperature may drop to the 40s (4–9 °C) in the mountains, in the 50s (10–15 °C) in the valleys, and in the low 60s (16 °C to 20 °C) in the coastal zone. In general the climate in the dry season is sunny, with little change from day to day. February and March are often quite dry, sunny and hot. Sun. The sunrise varies from 5:30 a.m. in summer and 7:00 a.m. in winter . Sunset varies between 5:40 p.m. in winter and 7:10 p.m. in summer. Puerto Rico does not use daylight saving time. The ultraviolet index or UV index varies from 10+ in the summer and a maximum of 7 in winter.