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Average Weather in Rockland Maine, United States

In Rockland, the temperature typically varies from 14°F to 75°F over the course of the year, and is rarely below -1°F or above 83°F.

The warm season lasts for 3.4 months, from June 6 to September 19, with an average daily high temperature above 66°F. The hottest day of the year is July 26, with an average high of 75°F and low of 59°F.

The cold season lasts for 3.4 months, from December 5 to March 16, with an average daily high temperature below 40°F. The coldest day of the year is January 29, with an average low of 14°F and high of 31°F.

Average High and Low Temperature

The daily average high (red line) and low (blue line) temperature with percentile bands, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

12 AM4 AM8 AM12 PM4 PM8 PM12 AMJanFebMarAprMayJunJulAugSepOctNovDecfreezingfreezingchillychillycoldcoldcoolcoolcomfortablecomfortable
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Sun

The length of the day in Rockland varies significantly over the course of the year. In 2017, the shortest day is December 21, with 8 hours, 52 minutes of daylight; the longest day is June 21, with 15 hours, 30 minutes of daylight.

Hours of Daylight and Twilight

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 4:52 AM on June 15, and the latest sunrise is 2 hours, 25 minutes later at 7:17 AM on November 4. The earliest sunset is at 3:57 PM on December 9, and the latest sunset is 4 hours, 26 minutes later at 8:23 PM on June 26.

Daylight saving time (DST) is observed in Rockland during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.

Sunrise & Sunset with Twilight and Daylight Saving Time

The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Clouds

In Rockland, 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 Rockland begins around June 26 and lasts for 4.2 months, ending around November 1. On September 3, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 64% of the time, and overcast or mostly cloudy 36% of the time.

The cloudier part of the year begins around November 1 and lasts for 7.8 months, ending around June 26. On May 16, the cloudiest day of the year, the sky is overcast or mostly cloudy 57% of the time, and clear, mostly clear, or partly cloudy 43% of the time.

Cloud Cover

clearerclearercloudiercloudiercloudiercloudier0%10%20%30%40%50%60%70%80%90%100%JanFebMarAprMayJunJulAugSepOctNovDecMay 1657%May 1657%Sep 336%Sep 336%Jun 2647%Jun 2647%Nov 147%Nov 147%overcastovercastmostly cloudymostly cloudymostly clearmostly clearclearclear
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

Rockland 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 22% 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 Rockland changes throughout the year.

Rain alone is the most common for 11 months, from February 5 to January 21. The highest chance of a day with rain alone is 31% on June 14.

Snow alone is the most common for 2.1 weeks, from January 21 to February 5. The highest chance of a day with snow alone is 10% on January 29.

Daily Chance of Precipitation

rainrainrainrain0%10%20%30%40%50%60%70%80%90%100%JanFebMarAprMayJunJulAugSepOctNovDecDec 1132%Dec 1132%Aug 3022%Aug 3022%Jan 2126%Jan 2126%mixedmixedrainrainsnowsnow
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

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 in the year. Rockland experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year in Rockland. The most rain falls during the 31 days centered around November 6, with an average total accumulation of 4.4 inches.

The least rain falls around January 30, with and average total accumulation of 1.9 inches.

Average Monthly Rainfall

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Snowfall

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 in the year. Rockland experiences significant seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 5.8 months, from October 28 to April 23, 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 23, with an average total liquid-equivalent accumulation of 1.2 inches.

The snowless period of the year lasts for 6.2 months, from April 23 to October 28. The least snow falls around July 21, with an average total liquid-equivalent accumulation of 0.0 inches.

Average Liquid-Equivalent Monthly Snowfall

The average liquid-equivalent snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

Rockland experiences some seasonal variation in the perceived humidity.

The muggier period of the year lasts for 2.6 months, from June 23 to September 10, during which time the comfort level is muggy, oppressive, or miserable at least 3% of the time. The muggiest day of the year is August 2, with muggy conditions 13% of the time.

The least muggy day of the year is March 6, when muggy conditions are essentially unheard of.

Humidity Comfort Levels

muggymuggy0%10%20%30%40%50%60%70%80%90%100%JanFebMarAprMayJunJulAugSepOctNovDecMar 60%Mar 60%Aug 213%Aug 213%Jun 233%Jun 233%Sep 103%Sep 103%muggymuggycomfortablecomfortabledrydry
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Rockland experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.2 months, from October 12 to April 19, with average wind speeds of more than 4.8 miles per hour. The windiest day of the year is January 31, with an average hourly wind speed of 6.4 miles per hour.

The calmer time of year lasts for 5.8 months, from April 19 to October 12. The calmest day of the year is August 8, with an average hourly wind speed of 3.3 miles per hour.

Average Wind Speed

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction in Rockland varies throughout the year.

The wind is most often from the north for 2.3 months, from February 9 to April 17, with a peak percentage of 39% on February 12. The wind is most often from the south for 5.7 months, from April 17 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 44% on January 5.

Wind Direction

WWNNSSWW0%20%40%60%80%100%JanFebMarAprMayJunJulAugSepOctNovDecwestwestsouthsoutheasteastnorthnorth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Rockland 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 3.0 months, from July 1 to October 2, with an average temperature above 55°F. The day of the year with the warmest water is August 14, with an average temperature of 59°F.

The time of year with cooler water lasts for 3.5 months, from January 11 to April 26, with an average temperature below 42°F. The day of the year with the coolest water is March 10, with an average temperature of 37°F.

Average Water Temperature

The daily average water temperature (purple line) with percentile bands, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences very significant seasonal variation over the course of the year.

The brighter period of the year lasts for 3.5 months, from May 9 to August 24, with an average daily incident shortwave energy per square meter above 5.7 kWh. The brightest day of the year is July 1, with an average of 6.8 kWh.

The darker period of the year lasts for 3.4 months, from October 31 to February 12, with an average daily incident shortwave energy per square meter below 2.5 kWh. The darkest day of the year is December 24, with an average of 1.4 kWh.

Average Daily Incident Shortwave Solar Energy

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Rockland are 44.104 deg latitude, -69.109 deg longitude, and 59 ft elevation.

The topography within 2 miles of Rockland contains only modest variations in elevation, with a maximum elevation change of 282 feet, and an average elevation above sea level of 57 feet. Within 10 miles contains very significant variations in elevation (1,378 feet). Within 50 miles also contains very significant variations in elevation (1,532 feet).

The area within 2 miles of Rockland is covered by water (29%), trees (27%), cropland (24%), and artificial surfaces (17%), within 10 miles by water (49%) and trees (44%), and within 50 miles by water (54%) and trees (41%).

Data Sources

This report illustrates the typical weather in Rockland, 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 5 weather stations near enough to contribute to our estimation of the temperature and dew point in Rockland.

For each station, the records are corrected for the elevation difference between that station and Rockland 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 Rockland is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Rockland and a given station.

The stations contributing to this reconstruction are: Knox County Regional Airport (94%, 4.1 kilometers, south), Augusta State Airport (1.7%, 60 kilometers, northwest), Waterville Robert Lafleur Airport (1.5%, 65 kilometers, northwest), Hancock County-Bar Harbor Airport (1.4%, 71 kilometers, northeast), and Bangor International Airport (1.1%, 81 kilometers, north).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .