Portland, Maine, experiences a humid continental climate. The city’s location in Southern Maine makes it a frequent target for winter storms moving up the Atlantic coast. On average, Portland receives a substantial amount of winter precipitation, with the official average annual snowfall total measured at the Portland International Jetport landing at approximately 68.7 inches. This figure places the city among the snowiest in the United States.
Average Annual Snowfall and Historical Records
The official average annual snowfall is 68.7 inches, calculated using the 30-year climate normal period (1991 to 2020) at the Portland International Jetport weather station. This average represents the typical seasonal accumulation, though the actual amount can fluctuate widely from one winter to the next. The historical data shows a significant range of variability in seasonal totals.
The greatest seasonal snowfall ever recorded in Portland history was 141.5 inches, which occurred during the winter season of 1970–1971. This record total is more than double the current average. In contrast, other seasons have been substantially lighter, with some years logging seasonal totals as low as 30 inches, demonstrating a difference of over 111 inches between the extremes.
Seasonal Distribution and Peak Months
Portland’s snow season typically stretches from late autumn into early spring. The first measurable snow often falls in November, and the final snowfall can occur as late as April. The snow-free period generally runs from May through September. The bulk of the accumulation happens during the mid-winter months.
January and February are the peak months for snowfall, consistently delivering the highest monthly totals based on the 1991-2020 normals. The three-month stretch from December through February is the core of the snow season.
- January averages approximately 18.6 inches of snow.
- February typically sees a total of about 16.6 inches.
- December also contributes a significant amount, averaging 14.6 inches.
- March usually sees a sharp drop-off, but still averages 13.6 inches.
Geographic Factors Shaping Portland’s Snow
Portland’s proximity to the Atlantic Ocean and its position relative to major storm tracks are the primary influences on its heavy snowfall. The city sits on the Gulf of Maine, which allows for the frequent development and intensification of weather systems known as Nor’easters. These storms move northeastward along the coast, drawing significant moisture from the relatively warmer Atlantic waters.
The interaction between cold, Arctic air masses and this available Atlantic moisture is the fuel for heavy snow events. As the cold air meets the warmer, moist air over the ocean, when a Nor’easter tracks just offshore, it often delivers the heaviest, wet snow to the coastal areas like Portland, sometimes resulting in well over a foot of accumulation from a single storm.