Average Weather in Belfast Maine, United States
In Belfast, the summers are comfortable, the winters are freezing, and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 12°F to 78°F and is rarely below -4°F or above 86°F.
Based on the tourism score, the best time of year to visit Belfast for warm-weather activities is from late June to early September.
The warm season lasts for 3.5 months, from June 3 to September 18, with an average daily high temperature above 68°F. The hottest day of the year is July 27, with an average high of 78°F and low of 60°F.
The cold season lasts for 3.3 months, from December 3 to March 14, with an average daily high temperature below 38°F. The coldest day of the year is January 29, with an average low of 12°F and high of 29°F.
Average High and Low Temperature
Average Hourly Temperature
In Belfast, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Belfast begins around June 26 and lasts for 4.1 months, ending around October 30. On September 3, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 63% of the time, and overcast or mostly cloudy 37% of the time.
The cloudier part of the year begins around October 30 and lasts for 7.9 months, ending around June 26. On May 16, the cloudiest day of the year, the sky is overcast or mostly cloudy 58% of the time, and clear, mostly clear, or partly cloudy 42% of the time.
Cloud Cover Categories
Belfast does not experience significant seasonal variation in the frequency of wet days (i.e., those with greater than 0.04 inches of liquid or liquid-equivalent precipitation). The frequency ranges from 23% to 32%, with an average value of 28%.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation in Belfast changes throughout the year.
Rain alone is the most common for 10 months, from February 20 to December 22. The highest chance of a day with rain alone is 32% on June 13.
Snow alone is the most common for 2.0 months, from December 22 to February 20. The highest chance of a day with snow alone is 13% on January 1.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Belfast experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Belfast. The most rain falls during the 31 days centered around October 23, with an average total accumulation of 4.1 inches.
The least rain falls around January 23, with an average total accumulation of 1.4 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Belfast experiences significant seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 6.0 months, from October 25 to April 25, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 11, with an average total liquid-equivalent accumulation of 1.5 inches.
The snowless period of the year lasts for 6.0 months, from April 25 to October 25. The least snow falls around July 21, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Belfast varies significantly over the course of the year. In 2018, the shortest day is December 21, with 8 hours, 50 minutes of daylight; the longest day is June 21, with 15 hours, 33 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 4:50 AM on June 15, and the latest sunrise is 2 hours, 25 minutes later at 7:16 AM on November 3. The earliest sunset is at 3:56 PM on December 9, and the latest sunset is 4 hours, 28 minutes later at 8:24 PM on June 26.
Daylight saving time (DST) is observed in Belfast during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.
Sunrise & Sunset with Twilight and Daylight Saving Time
Belfast experiences some seasonal variation in the perceived humidity.
The muggier period of the year lasts for 2.8 months, from June 19 to September 12, during which time the comfort level is muggy, oppressive, or miserable at least 4% of the time. The muggiest day of the year is August 2, with muggy conditions 16% of the time.
The least muggy day of the year is December 1, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
The average hourly wind speed in Belfast experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.3 months, from October 18 to April 26, with average wind speeds of more than 6.4 miles per hour. The windiest day of the year is February 25, with an average hourly wind speed of 8.2 miles per hour.
The calmer time of year lasts for 5.7 months, from April 26 to October 18. The calmest day of the year is August 1, with an average hourly wind speed of 4.6 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Belfast varies throughout the year.
The wind is most often from the north for 2.5 months, from February 9 to April 24, with a peak percentage of 38% on March 4. The wind is most often from the south for 5.5 months, from April 24 to October 7, with a peak percentage of 44% on July 2. The wind is most often from the west for 4.1 months, from October 7 to February 9, with a peak percentage of 42% on January 1.
Belfast is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average water temperature experiences significant seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.3 months, from July 1 to October 10, with an average temperature above 53°F. The day of the year with the warmest water is August 15, with an average temperature of 58°F.
The time of year with cooler water lasts for 3.4 months, from January 13 to April 24, with an average temperature below 41°F. The day of the year with the coolest water is March 11, with an average temperature of 37°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Belfast throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Belfast for general outdoor tourist activities is from late June to early September, with a peak score in the second week of August.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Belfast for hot-weather activities is from mid July to mid August, with a peak score in the last week of July.
The growing season in Belfast typically lasts for 5.5 months (165 days), from around April 28 to around October 10, rarely starting before April 12 or after May 14, and rarely ending before September 25 or after October 26.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Belfast should appear around May 13, only rarely appearing before May 3 or after May 22.
Growing Degree Days
The brighter period of the year lasts for 3.5 months, from May 8 to August 24, with an average daily incident shortwave energy per square meter above 5.6 kWh. The brightest day of the year is July 1, with an average of 6.7 kWh.
The darker period of the year lasts for 3.4 months, from October 31 to February 11, with an average daily incident shortwave energy per square meter below 2.5 kWh. The darkest day of the year is December 17, with an average of 1.4 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Belfast are 44.426 deg latitude, -69.006 deg longitude, and 148 ft elevation.
The topography within 2 miles of Belfast contains only modest variations in elevation, with a maximum elevation change of 338 feet and an average elevation above sea level of 123 feet. Within 10 miles contains only modest variations in elevation (1,030 feet). Within 50 miles also contains very significant variations in elevation (1,532 feet).
The area within 2 miles of Belfast is covered by trees (58%), water (22%), and artificial surfaces (13%), within 10 miles by trees (69%) and water (25%), and within 50 miles by trees (60%) and water (33%).
This report illustrates the typical weather in Belfast, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Belfast.
For each station, the records are corrected for the elevation difference between that station and Belfast according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Belfast is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Belfast and a given station.
The stations contributing to this reconstruction are: Knox County Regional Airport (31%, 41 kilometers, south); Bangor International Airport (27%, 44 kilometers, north); Hancock County-Bar Harbor Airport (22%, 51 kilometers, east); and Waterville Robert Lafleur Airport (20%, 54 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .