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May Weather in Boston, United States

Last updated: June 24, 2025

In May, the average temperature in Boston, United States is a pleasant 25°C (76°F), but be prepared for a range; it can drop to as low as 9°C (49°F) and soar up to 39°C (102°F). Expect about 74 mm (2.9 in) of precipitation over 8 days, with an average humidity of 73%, making the climate feel quite tropical.

May Temperature in Boston

In May in Boston, the average temperature is 25°C (76°F). Maximums can reach 39°C (102°F), and minimums can drop as low as 9°C (49°F). Overall, travelers can expect warm days with a chance of cooler evenings, so it's wise to prepare for a variety of temperatures.

May Weather in Boston: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in Boston, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Boston, May typically has an average temperature of 25°C (76°F), with highs reaching up to 39°C (102°F) and lows dropping to around 9°C (49°F).
JanFebMarAprMayJunJulAugSepOctNovDec535963687680818180736056
Data source: Temperature data for Boston generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

May Precipitation in Boston

In Boston in May, the precipitation amount is 74 mm (2.9 in) over a period of 8 days.

May Precipitation Trends in Boston

The chart displays monthly precipitation patterns in Boston, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Boston, May typically receives around 74 mm (2.9 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec72965280741571481371107350118
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Boston

In Boston in May, humidity is 73%. With an average temperature of 25°C (76°F), this humidity feels like walking through a warm, wet blanket, making travel feel sluggish and sticky, as the air clings to your skin and saps your energy while exploring.

May Average Humidity in Boston

This chart illustrates the average monthly humidity levels in Boston, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Boston is approximately 73%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%82%80%76%73%74%80%79%83%77%84%88%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Boston

In Boston in May, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Boston.

Maximum UV Index Levels in Boston for May

The chart shows the monthly maximum UV Index (UVI) for Boston in May, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In May, the maximum UV index in Boston typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec589101111111110864
Data source: Boston May UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How May Weather in Boston Compares to Other Months

Weather in Boston varies notably across the year, with each month offering distinct climate conditions. This page compares May’s weather to other months in Boston, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Boston, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather12°C (54°F)72 mm (2.8 inches)85%moderate
February Weather15°C (60°F)96 mm (3.8 inches)82%very high
March Weather17°C (64°F)52 mm (2.1 inches)80%very high
April Weather20°C (69°F)80 mm (3.1 inches)76%very high
May Weather25°C (76°F)74 mm (2.9 inches)73%extreme
June Weather27°C (80°F)157 mm (6.2 inches)74%extreme
July Weather27°C (81°F)148 mm (5.8 inches)80%extreme
August Weather27°C (82°F)137 mm (5.4 inches)79%extreme
September Weather26°C (80°F)110 mm (4.3 inches)83%very high
October Weather23°C (74°F)73 mm (2.9 inches)77%very high
November Weather16°C (61°F)50 mm (2.0 inches)84%high
December Weather13°C (56°F)117 mm (4.6 inches)88%moderate

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