Snowfall statistics at 11 weather stations in the characterization area are 

 summarized in table 2-4. Variability in snowfall depths from year to year can 

 be substantial at all stations. Minimum amounts vary from 24 inches (61 cm) 

 at Ellsworth to 46 inches (117 cm) at Lewiston, while maximum amounts range 

 from 106 inches (269 cm) at Augusta to 182 inches (462 cm) at Bangor. These 

 statistics generally apply to a period of 30 years. In an average year, the 

 number of days with snowfall >1 inch (2.5 cm) varies from 18 to 23, while that 

 for snowfall >4 inches (10 cm) varies from 5 to 8 days throughout the coastal 

 zone. Average snowfall >10 inches (25.4 cm) does not exceed 1 day/year at any 

 station. 



Average monthly snowfall is highest in February at nearly all stations. The 

 greatest amount of snow falls between December and March. The snowfall 

 distribution at Bangor, shown in figure 2-15, is typical of the entire area, 

 although a greater amount of snow falls at Bangor. A comparison of snowfall 

 and total precipitation data for November and December indicates that most of 

 the precipitation during these months is rain. Consequently, natural water 

 storage areas are replenished at the start of most winters. The ensuing cold 

 temperatures will cause much of this water to be held as ice until the first 

 major thaws. This, combined with the melting of accumulated snowfall, results 

 in spring flooding of wetlands. 



The period of maximum snowfall is also the period of maximum snow depth and 

 maximum continuous snow cover in coastal Maine. Maximum snow cover duration 

 averages about 50 days on the immediate coast and up to 70 or 80 days at the 

 inland boundary of the coastal zone. Yearly variability in snow cover is 

 high, with the shortest maximum duration averaging 7 days on the coast and 14 

 days inland. The longest average maximum snow cover duration ranges between 

 11 and 132 days. Average maximum snow depths range from 14 to 25 inches (36 

 to 64 cm). Although a significant amount of snow cover is present during most 

 winters, an abnormally clear season occurs approximately every 6 to 8 years. 

 Snow cover duration and depth at nine locations in the characterization area 

 are summarized in table 2-5. 



Freeze penetration and the growing season . The length of the growing 

 season commonly is determined by the length of the average freeze-free period. 

 Some vegetation is damaged by temperatures 32°F (0°C). The mean duration of 

 the freeze-free period at 11 weather stations in coastal Maine is given in 

 table 2-6. The range is 131 to 174 days. 



The four stations with the longest period of record are Eastport, Woodland, 

 Bar Harbor, and Lewiston. Woodland, near the inland boundary of the coastal 

 zone and the most northerly station, exhibits the shortest growing season and 

 Eastport the longest. Bar Harbor and Lewiston are in the middle of this range 

 but are closer to the Eastport value. These figures indicate that while 

 distances from the coast can be an important factor in the growing season, 

 other local effects may be equally important. 



A measure of the severity of the winter season is the freezing index. This 

 index is based on the computation of degree-days. Degree-days are a measure 

 of the number of degrees below 32°F (0°C) of the average (of maximum and 

 minimum) temperature for a given day. For example, an average daily 

 temperature of 15°F (-9°C) yields a value of 17 degree-days. The air-freezing 

 index for a given freezing season is the number of degree-days between the 



2-28 



