This report describes the typical weather at the Nantucket Memorial Airport (Nantucket, 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.
Nantucket, Massachusetts has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by oceans and seas (98%).
Over the course of a year, the temperature typically varies from 26°F to 76°F and is rarely below 14°F or above 81°F.
The warm season lasts from June 15 to September 22 with an average daily high temperature above 68°F. The hottest day of the year is July 26, with an average high of 76°F and low of 64°F.
The cold season lasts from December 9 to March 22 with an average daily high temperature below 45°F. The coldest day of the year is January 26, with an average low of 26°F and high of 37°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:11 hours of daylight; the longest day is June 20 with 15:09 hours of daylight.
The earliest sunrise is at 5:06am on June 13 and the latest sunset is at 8:18pm on June 27. The latest sunrise is at 7:14am on November 3 and the earliest sunset is at 4:11pm on December 7.
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.
The median cloud cover ranges from 58% (partly cloudy) to 80% (partly cloudy). The sky is cloudiest on May 31 and clearest on September 22. The clearer part of the year begins around August 11. The cloudier part of the year begins around November 14.
On September 22, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 44% of the time, and overcast or mostly cloudy 40% of the time.
On May 31, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 58% of the time, and clear or mostly clear 27% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around January 8, occurring in 47% of days. Precipitation is least likely around August 13, occurring in 25% of days.
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 44% of those days with precipitation. It is most likely around April 26, when it is observed during 21% of all days.
Moderate rain is the most severe precipitation observed during 20% of those days with precipitation. It is most likely around December 3, when it is observed during 9% of all days.
Light snow is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around February 2, when it is observed during 16% of all days.
During the warm season, which lasts from June 15 to September 22, there is a 26% 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 (52% of days with precipitation have at worst light rain), moderate rain (22%), heavy rain (13%), and thunderstorms (11%).
During the cold season, which lasts from December 9 to March 22, there is a 44% 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 (31% of days with precipitation have at worst light snow), light rain (31%), moderate rain (16%), and moderate snow (11%).
The likelihood of snow falling is highest around February 2, occurring in 24% of days. The season in which it is relatively likely for snow to fall spans from December 1 to April 5.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 57% (mildly humid) to 99% (very humid) over the course of the year, rarely dropping below 33% (comfortable) and reaching as high as 100% (very humid).
The air is driest around February 19, at which time the relative humidity drops below 68% (mildly humid) three days out of four; it is most humid around July 22, exceeding 100% (very humid) three days out of four.
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 16°F (dry) to 68°F (muggy) and is rarely below -0°F (dry) or above 73°F (very muggy).
There are two periods in the year that are most comfortable: The first is between May 15 and July 8 and the second is between August 26 and October 23. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 4 mph to 22 mph (light breeze to fresh breeze), rarely exceeding 30 mph (strong breeze).
The highest average wind speed of 14 mph (moderate breeze) occurs around March 12, at which time the average daily maximum wind speed is 22 mph (fresh breeze).
The lowest average wind speed of 10 mph (gentle breeze) occurs around August 7, at which time the average daily maximum wind speed is 15 mph (moderate breeze).