The ocean, trade winds, and the terrain’s high elevation provide temperate conditions. Mountain areas are cool; the plains and valleys are warmer and more humid. The average annual temperature in the Dominican Republic is 24ºC (75ºF). The mean annual temperature along the coastal plain is 26°C (78°F), while the mean annual temperature in the Central Cordillera is 20°C (68°F). There is relatively little seasonal change, except for variations in rainfall.
Relative humidity remains uniform throughout the year at 80 percent. Rainfall is moderate except on the Samana Peninsula in the northeastern part of the Dominican Republic and in the mountains around Santiago, where as much as 2,640 millimeters (100 inches) falls per year. Most rain falls during May through November, producing an annual mean rainfall of 1,390 millimeters (955 inches).
Northeast trade winds, tropical cyclones, easterly waves, and fronts affect the climate year-round. Hurricanes are a significant threat in the Dominican Republic, particularly from mid-July through October. An average of eight hurricanes per year strikes the Caribbean region.
The Dominican Republic will be among the worst hit by the effects of climate change, according to the Global Climate Risk Index 2014. The World Bank has called coastal erosion in the Caribbean a “grave challenge" that will continue to worsen as global temperatures rise. All regions experience strong inter-annual rainfall variability linked to El Niño-Southern Oscillation (ENSO) as well as a decadal variability related to the Tropical Atlantic; decadal variability in the Tropical Atlantic also strongly affects the frequency of hurricanes.
The capital, Santo Domingo, will be among the five cities in the world most affected by rising sea levels, according to current predictions. The city’s poorest residents will be most vulnerable to flooding from storm surges and rain fueled by warmer temperatures. In response, an ambitious government-sponsored climate adaptation project aims to relocate the neighborhood's most vulnerable families to higher ground.
USAID’s African and Latin American Resilience to Climate Change (ARCC) project conducted a climate change vulnerability assessment of the Dominican Republic in 2012-13. In the medium and long term, this Caribbean country is projected to see less rainfall in May - usually a rainy month - and more in December, which is usually a dry month. Temperatures are expected to rise .5-1°C and 1-2.5 °C by 2030 and 2050, respectively.
Sea level rise will likely exacerbate coastal flooding and beach erosion. Tropical storms will become more intense as ocean and global temperatures continue to rise, likely exacerbating damage from coastal flooding and erosion. These effects will impact coastal communities, businesses and agriculture.
Increasing temperatures will continue to strain agricultural systems and groundwater availability and quality due to the possibility of hotter and drier conditions in Yaque del Norte, where precipitation is projected to slightly decrease. Increased frequency and intensity of flooding due to the combination of more intense storms and environmental degradation is likely to disproportionately affect already sensitive systems (e.g., livelihoods on the edge, people in poverty, coastal infrastructure).
Residential households and the agriculture and tourism sectors heavily depend on ground and surface water supply, which are sensitive to localized land use and likely to experience decreasing recharge and quality due to evaporation and salt water intrusion. Inadequate sewage management further compromises water quality. In the absence of adequate sewage treatment facilities, most raw sewage is dumped into the aquifer through injection wells called “pozos filtrantes" or directly into rivers and the ocean, worsening water quality and increasing health risks.
As a small island developing state, and being located in an area of intense hurricane activity, the Dominican Republic is threatened constantly by hydro-meteorological events such as tropical storms, droughts and hurricanes affecting human settlements and productive activities.
Damage associated with hydro-meteorological events over the years has left a trail of effects demanded beyond considerable efforts. In 1998, Hurricane Georges caused losses and damages equivalent to 14% of Gross Domestic Product (GDP) in 1997. The tropical storms Olga and Noel in 2007 forced the government to adjust its priorities and the economy, causing losses and damages of 1.2% of GDP and 5.3% of the national budget. Additionally, the damage caused by many other disasters including floods, landslides and droughts have not been quantified.
The impacts of some extreme events have meant economic losses in the order of USD 9,470 million, and the most affected sectors have been: agriculture, transportation, energy, housing, education, industry and trade, sanitation, drainage, health and environment. These statistics refer to major events that cause disasters, but smaller and recurrent events can cause major damage to property, livelihoods and crops. However, certain gaps in the historical record of medium and small events persist, and the amount is estimated to be equal to half of the loss and damage of the biggest events.
Alongside bringing in tourist dollars, healthy coral reefs, seagrasses and salt-tolerant mangroves provide habitats for many species that generate an income for fishermen — from spiny lobsters in Belize to bonefish in the Bahamas. Reefs can also act like breakwaters to dramatically reduce wave strength, while mangroves can buffer against hurricane winds and storm surges. Coral reefs can slash up to 97 percent of the wave energy that would otherwise hit the shoreline, while a 100-meter-wide (330 feet) band of mangrove can cut wave height by up to two-thirds.