Boston Weather in August

August continues the warm and sunny weather for Boston, Massachusetts. Indeed, Boston's August climate is typically drier and less cloudy than other summer months.

This page gives detailed information on the typical August temperature, precipitation, sun, humidity, wind and storms for Boston. The numbers here are historical averages based on climate data gathered at Boston's Logan International Airport, located on the waterfront next to Boston Harbor.

Temperature Weather iconTemperature

80 °F August average high 27 °C
65 °F August average low 18 °C
18 days 80 °F max. or more (27 °C)
27 days 70 °F min. or less (21 °C)

Nearly every day in August warms to over 70 degrees Fahrenheit (21 degrees Celsius) in Boston. The city averages 4 days this month when the thermometer reaches into the 90s °F (over 32 °C). Temperatures above 100 °F (38 °C) are not expected here during August.

At night, the thermometer dips to 60 °F (16 °C) or below on 5 days. August normally doesn't get as cold as 50 °F (10 °C).

Rainy Weather iconRain

3.2 in total precipitation 82 mm
9 days of rain

Half the time, Boston receives 1.8 to 4.4 inches (45 to 110 mm) of rainfall in August. One in four years has drier weather, while another one in four is wetter. None of the precipitation falls as snow.

Sunny Weather iconSun

65 % sunshine
9 days clear skies

The sun's rays reach the ground in Boston during 65 percent of daylight hours on average in August, for a total of 278 hours in the month. Typically on 9 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in August at Boston lasts for 13 hours and 49 minutes a day on average. The longest day of the month is the 1st with 14 hours and 26 minutes of daylight. By the end of the month, the days have shortened to 13:10 from sunrise to sunset. These durations of daylight can vary by a minute or two from year to year.

Humid Weather iconHumidity

71 % August average humidity

The relative humidity in Boston during August usually peaks at 82 percent in the morning then drops to 59 percent by early afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 79 82 77 64 59 61 69 76

Windy Weather iconWind

10.8 mph August wind speed average 17.4 kph

The wind at Boston is calmest overall during August.

Stormy Weather iconStorms

2 days rainfall of 0.5 inches (13 mm) or more
3 days with thunderstorms in August
6 % chance a named storm approaches

There's a 2 percent probability that a hurricane will approach within 100 miles (165 km) of Boston during August. The chance of a major hurricane (category 3 to 5) reaching the area is 1 percent.


The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals. The named storm probabilities come from the Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division.

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