Under the Köppen climate classification, Stamford has a temperate climate (Cfa), with long, hot summers, and cool to cold winters, with precipitation spread fairly evenly throughout the year. Stamford, like the rest of coastal Connecticut, lies in the broad transition zone between the colder continental climates of the northern United States and southern Canada to the north, and the warmer temperate and subtropical climates of the middle and south Atlantic states to the south.
The warm/hot season in Stamford is from mid-April through early November. Late day thundershowers are common in the hottest months (June, July, August, September), despite the mostly sunny skies. The cool/cold season is from late November though mid March. Winter weather is far more variable than summer weather along the Connecticut coast, ranging from sunny days with higher temperatures to cold and blustery conditions with occasional snow. Like much of the Connecticut coast and nearby Long Island, NY, some of the winter precipitation is rain or a mix and rain and wet snow in Stamford. Stamford averages about 30 inches (75 cm) of snow annually, compared to inland areas like Hartford and Albany which average 45–60 inches (110–150 cm) of snow annually.
Although infrequent, tropical cyclones (hurricanes/tropical storms) have struck Connecticut and the Stamford metropolitan area. Hurricane landfalls have occurred along the Connecticut coast in 1903, 1938, 1944, 1954 (Carol), 1960 (Donna), Hurricane Gloria in 1985, and Hurricane Sandy in 2012.
Stamford lies in USDA garden zone 7a. Stamford averages about 90 days annually with freeze. Coastal Connecticut is the broad transition zone where so-called “subtropical indicator” plants and other broadleaf evergreens can successfully be cultivated. As such, Southern Magnolias, Needle Palms, Windmill palm, Loblolly Pines, and Crape Myrtles are grown in private and public gardens. Like much of coastal Connecticut, Long Island, New York, and coastal New Jersey, the growing season is rather long in Stamford—averaging 210 days from April 8 to November 5 according to the National Weather Service in Bridgeport.