Source: The Library Of Congress Country Studies
The Dominican Republic has primarily a tropical climate, with more diurnal and local variations in temperature than seasonal ones, and with seasonal variability in the abundance of rainfall. The average annual temperature is 25° C, ranging from 18° C at an altitude of over 1,200 meters to 28° C at an altitude of 10 meters. Highs of 40° C are common in protected valleys, as are lows of zero in mountainous areas. In general, August is the hottest month, and January and February are the coldest ones.
Seasons, however, vary more as a function of rainfall than of temperature. Along the northern coast, the rainy season lasts from November through January. In the rest of the country, it runs from May through November; May is the wettest month. The dry season lasts from November through April; March is the driest month. The average annual rainfall for the country as a whole is 150 centimeters. This varies, however, from region to region, and ranges from 35 centimeters in the Valle de Neiba to 274 centimeters in the Cordillera Oriental. In general, the western part of the country, including the interior valleys, receives the least rain.
Tropical cyclones--such as tropical depressions, tropical storms, and hurricanes--occur on the average of once every two years in the Dominican Republic. Over 65 percent of the storms strike the southern part of the country, especially along the Hoya de Enriquillo. The season for cyclones lasts from the beginning of June to the end of November; some cyclones occur in May and December, but most take place in September and October. Hurricanes usually occur from August through October. They may produce winds greater than 200 kilometers per hour and rainfall greater than 50 centimeters in a twenty-four-hour period.
Data as of 1989