Boston Weather in May

Boston, Massachusetts has pleasantly mild weather in May. Most days have temperatures over 60 degrees Fahrenheit (16 degrees Celsius). But the rain falls more often in May than it does in other months.

This page gives detailed information on the typical May 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

67 °F May average high 19 °C
50 °F May average low 10 °C
12 days 70 °F max. or more (21 °C)
18 days 50 °F min. or less (10 °C)

Nearly every day in May warms to over 50 °F (10 °C) in Boston. The city averages 4 days this month when the thermometer reaches into the 80s °F (over 26 °C). The temperature can rise above 90 °F (32 °C) during May, but that doesn't happen every year.

This month the thermometer dips to 40 °F (4 °C) or below for an average of one night. But May does not normally get as cold as 32 °F (0 °C).

Rainy Weather iconRain

3.3 in total precipitation 83 mm
12 days of rain

Half the time, Boston receives 2.3 to 3.5 inches (59 to 88 mm) of rainfall in May. One in four years has drier weather, while another one in four is wetter. None of the precipitation falls as snow.

Sunny Weather iconSun

58 % sunshine
6 days clear skies

The sun's rays reach the ground in Boston during 58 percent of daylight hours on average in May, for a total of 262 hours in the month. Typically on 6 days this month the sky is mainly clear, with at most 30 percent cloud cover. May has fewer clear days than any other month here.

Sunlight in May at Boston lasts for 14 hours and 37 minutes a day on average. The shortest day of the month is the 1st with 14 hours and 5 minutes of daylight. By the end of the month, the days have lengthened to 15:04 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

97 % May average humidity

The relative humidity in Boston during May usually peaks at 77 percent in the morning then drops to 58 percent by early afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 74 77 71 61 58 58 64 70

Windy Weather iconWind

12.0 mph May wind speed average 19.3 kph

May is an average month in Boston for wind speed.

Stormy Weather iconStorms

2 days rainfall of 0.5 inches (13 mm) or more
2 days with thunderstorms in May

With winter over and the tropical storm season yet to begin, any storms passing through Boston during May are rain or thunderstorms.


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.

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