Average Weather For Boston, Massachusetts, USA

Location

This report describes the typical weather at the Logan International Airport (Boston, Massachusetts, United States) weather station over the course of an average year. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.

Boston, Massachusetts has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by forests (51%), oceans and seas (26%), and built-up areas (21%).

Temperature

Over the course of a year, the temperature typically varies from 22°F to 82°F and is rarely below 8°F or above 92°F.

Daily High and Low Temperature

The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

The warm season lasts from June 5 to September 14 with an average daily high temperature above 73°F. The hottest day of the year is July 14, with an average high of 82°F and low of 67°F.

The cold season lasts from December 5 to March 14 with an average daily high temperature below 45°F. The coldest day of the year is January 19, with an average low of 22°F and high of 35°F.

Fraction of Time Spent in Various Temperature Bands

The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

Sun

The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:04 hours of daylight; the longest day is June 20 with 15:17 hours of daylight.

Daily Hours of Daylight and Twilight

The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

The earliest sunrise is at 5:06am on June 14 and the latest sunset is at 8:26pm on June 26. The latest sunrise is at 7:21am on November 3 and the earliest sunset is at 4:11pm on December 9.

Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.

Daily Sunrise & Sunset with Twilight and Daylight Savings Time

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight savings time are indicated by the "DST" labels.

Clouds

The median cloud cover ranges from 58% (partly cloudy) to 80% (partly cloudy). The sky is cloudiest on April 27 and clearest on September 13. The clearer part of the year begins around July 3. The cloudier part of the year begins around November 14.

Median Cloud Cover

The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

On September 13, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 58% of the time, and overcast or mostly cloudy 42% of the time.

On April 27, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 70% of the time, and clear or mostly clear 30% of the time.

Cloud Cover Types

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around January 4, occurring in 51% of days. Precipitation is least likely around September 13, occurring in 38% of days.

Probability of Precipitation at Some Point in the Day

The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

Over the entire year, the most common forms of precipitation are light rain, moderate rain, and light snow.

Light rain is the most severe precipitation observed during 34% of those days with precipitation. It is most likely around May 15, when it is observed during 23% of all days.

Moderate rain is the most severe precipitation observed during 19% of those days with precipitation. It is most likely around May 13, when it is observed during 13% of all days.

Light snow is the most severe precipitation observed during 15% of those days with precipitation. It is most likely around January 12, when it is observed during 21% of all days.

Types of Precipitation Throughout the Year

Relative frequency of various types of precipitation over the course of a typical year.

During the warm season, which lasts from June 5 to September 14, there is a 41% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (40% of days with precipitation have at worst light rain), moderate rain (23%), thunderstorms (22%), and heavy rain (10%).

During the cold season, which lasts from December 5 to March 14, there is a 49% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light snow (36% of days with precipitation have at worst light snow), light rain (20%), moderate snow (13%), and moderate rain (11%).

Warm Season Precipitation

Cold Season Precipitation

Relative frequency of various types of precipitation during the warm and cold seasons respectively.

Snow

The likelihood of snow falling is highest around January 13, occurring in 34% of days. The season in which it is relatively likely for snow to fall spans from November 16 to April 9.

Probability of Snow Fall Being Reported in a Given Day

Probability that snow will be reported at least once in a given day. The season is defined as the period during which the probability is greater than one third the maximum probability.

During peak snow season, accumulation at this location on a given day is just less likely than not. The chances of there being snow on the ground are highest around January 30, occurring 39% of the time. The season in which snow is relatively likely to be on the ground spans from December 10 to March 21.

Chance of at Least Some Snow on the Ground

The probability that there is snow on the ground. The season is defined as the period during which the probability is greater than one third of the maximum probability.

The snow is typically at its deepest on May 9, with a median depth of 11.6"; the depth exceeds 16.7" only one year out of ten.

Snow Depth When there is Snow on the Ground

The median depth of snow during times when there is at least some snow on the ground, with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Humidity

The relative humidity typically ranges from 43% (comfortable) to 89% (very humid) over the course of the year, rarely dropping below 21% (dry) and reaching as high as 100% (very humid).

The air is driest around April 15, at which time the relative humidity drops below 56% (mildly humid) three days out of four; it is most humid around September 23, exceeding 83% (humid) three days out of four.

Relative Humidity

The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

Dew Point

Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.

Over the course of a year, the dew point typically varies from 9°F (dry) to 67°F (muggy) and is rarely below -9°F (dry) or above 73°F (very muggy).

There are two periods in the year that are most comfortable: The first is between May 13 and July 11 and the second is between August 16 and October 13. The air feels neither too dry nor too muggy during these periods.

Dew Point

The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

Over the course of the year typical wind speeds vary from 4 mph to 20 mph (light breeze to fresh breeze), rarely exceeding 28 mph (strong breeze).

The highest average wind speed of 13 mph (moderate breeze) occurs around March 5, at which time the average daily maximum wind speed is 20 mph (fresh breeze).

The lowest average wind speed of 10 mph (gentle breeze) occurs around August 5, at which time the average daily maximum wind speed is 16 mph (moderate breeze).

Wind Speed

The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
The wind is most often out of the west (20% of the time), north west (17% of the time), south west (16% of the time), north (11% of the time), south (11% of the time), and east (11% of the time).

Wind Directions Over the Entire Year

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.