Climate of Rhode Island

Rhode Island – the smallest U.S. state – shares the southeastern corner of New England with a portion of Massachusetts and occupies a total of 1,531 square miles (1,074 square miles of land and 457 square miles of water). Notably, Rhode Island has the third highest ratio of water area to total area of any state due to the unique shoreline of Narragansett Bay.

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Topography

The climate of Rhode Island is greatly influenced by the state’s unique topography. Generally, the state is divided into two distinct topographical regions:

1. Coastal Lowlands: A low-lying region that extends from the southern shore and 5-7 miles inland from Narragansett Bay. Elevations of the coastal lowlands range from sea level (0 feet) to 200 feet. This area also includes all small islands and Block Island, approximately 10 miles offshore.
2. New England Uplands: The western two-thirds of Rhode Island consists of hilly uplands, rising 200-600 feet above sea level. The state’s highest point, Jerimoth Hill in Foster, crests at 812 feet above sea level.

Rhode Island’s greatest natural resource, Narragansett Bay, is the largest estuary in New England. Over 40 islands exist throughout Narragansett Bay. Several small rivers drain directly into Narragansett Bay, the largest of which is the Pawtuxet River. Other rivers that drain into Narragansett Bay are tidally influenced – these include the Providence, Seekonk, and Taunton rivers. In the southwest corner of the state, the Pawcatuck River drains into Little Narragansett Bay and subsequently into Block Island Sound.

Climatology

Rhode Island lies in the “prevailing westerlies”, a belt of eastwardly air which encircles the globe in middle latitudes. Embedded within this circulation are air masses which originate from higher (polar) and lower (subtropical) latitudes. These air masses interact to produce storm systems, all of which influence the state’s climate.

Any particular month in Rhode Island that experiences normal climate conditions is the exception rather than the rule, as the state’s climate does not result from any single controlling weather pattern.

The Köppen-Geiger Climate Classification, which is commonly used to categorize Earth's climate into five zones, places Rhode Island into the temperate (zone C) and continental (zone D) climates. In zones C and D, there is an equitable distribution of precipitation across the year (subzone f: no significant dry season).

Microclimates in Rhode Island

Microclimates are small areas where the local climate differs from the broader regional climate due to variations in topography, land cover, or prominent geographical features (i.e., the ocean). Rhode Island is home to several microclimates that experience noticeably distinct conditions compared to the state’s typical climate zones.

Providence Area

The capital city of Providence – including urbanized areas in nearby communities – has significantly more impervious surface than other parts of Rhode Island. Asphalt, concrete, and rooftops absorb heat better than forests or farmland. This is known as the urban heat island effect. In the summer, the ambient air temperature around Providence is often higher than other parts of northern Rhode Island.

Northwest Providence County

Older generations of Rhode Islanders may recall the phrase “No School Foster-Glocester”. Northwest Providence County, which lies in the continental climate zone, can receive substantially more snowfall than other areas of the state due to its higher elevation and location away from the coast. Average snowfall for January and February in Foster is 5” greater than Warwick, while March snowfall in Foster is nearly double.

Southwest Washington County

Southwestern parts of Washington County (4-10 miles from the coast) exhibit a coolness not suggested by the area’s low elevation or proximity to the ocean. Here, the annual minimum temperature is less than 41°F. Rhode Island’s all-time coldest temperature of -28°F was recorded in Richmond, a mere 6 miles from the Atlantic Ocean. The likely reason for this microclimate is the area’s exposure to cold northwest winds during the winter months without the temperature-moderating effect of Narragansett Bay.

Southern Coastline and Block Island

The coastline of southern Rhode Island – including Block Island – is strongly influenced by the ocean. Offshore water temperatures remain relatively cool (60s-70s) during the early summer months, which keep the immediate coastline chillier than a few miles inland. When a humid airmass arrives, fog often forms and covers the coastline during the late night and early morning hours when the air temperature and the dewpoint are closest. This effect becomes less pronounced in late summer and early fall as ocean temperatures warm.