Massachusetts’ weather patterns, shaped by its coastal proximity and diverse inland topography, are a frequent topic of discussion. Many residents and visitors often wonder about the amount of sunshine the state receives each year.
What Counts as a Sunny Day?
Defining a “sunny day” involves specific meteorological criteria. The National Weather Service classifies a day as “clear” or “sunny” when one-eighth or less of the sky is covered by opaque clouds. Days with “mostly clear” or “mostly sunny” conditions typically have between one-eighth and three-eighths cloud cover.
A “partly sunny” day indicates that between three-eighths and five-eighths of the sky is covered by clouds, still allowing for significant periods of sunshine. Data sources like the National Climatic Data Center (NCDC) often track “percent of possible sunshine,” which measures the duration the sun is visible compared to the maximum possible daylight hours. This metric provides a comprehensive view beyond just completely cloudless days.
Massachusetts’ Statewide Sunny Day Averages
Massachusetts generally experiences a considerable number of days with at least some sunshine annually. Across various parts of the state, the average number of sunny or partly sunny days typically falls within a range of approximately 180 to 215 days per year.
For instance, Boston records around 200 to 213 sunny or partly sunny days each year. Moving inland to Worcester, the average is slightly lower, with approximately 197 such days annually.
Regional and Seasonal Differences Across the State
Sunshine patterns in Massachusetts exhibit notable variations depending on both geographical location and the time of year. Coastal areas, such as Boston and parts of Cape Cod, often benefit from ocean influences that can temper extreme temperatures and sometimes lead to slightly more consistent sunshine compared to inland regions. These coastal locations tend to experience milder conditions.
Western Massachusetts, including cities like Pittsfield, tends to have fewer sunny days, averaging between 182 and 188 days per year. This difference can be attributed to inland weather systems and the topographical effects of the Berkshire Mountains.
Seasonally, summer months consistently provide the most sunshine across Massachusetts. July and August are often the sunniest, with around 20 sunny or partly sunny days each during these months. June, September, and October also average approximately 19 days of sunshine. Conversely, the late autumn and winter months, particularly November and December, generally record the lowest number of sunny days, with November often being the least sunny month.