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May Weather in Portsmouth, United States

Last updated: June 24, 2025

In May, the average temperature in Portsmouth, United States hovers around 12°C (55°F). Visitors can expect a minimum of 4°C (39°F) and a maximum of 22°C (72°F) during this month. Precipitation reaches approximately 132 mm (5.2 in) over 14 days, contributing to an average humidity of 75%. Be prepared for a mix of cool and pleasant days!

May Temperature in Portsmouth

In May in Portsmouth, the average temperature is 12°C (55°F). Maximum temperatures can reach 22°C (72°F), while minimums can drop to as low as 4°C (39°F). It's advisable to pack layers to stay comfortable while exploring the local sights.

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

The chart illustrates May temperature patterns in Portsmouth, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Portsmouth, May typically has an average temperature of 12°C (55°F), with highs reaching up to 22°C (72°F) and lows dropping to around 4°C (39°F).
JanFebMarAprMayJunJulAugSepOctNovDec353638465464727267594839
Data source: Temperature data for Portsmouth 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 Portsmouth

In Portsmouth in May, the precipitation amount is 132 mm (5.2 in) over a span of 14 days.

May Precipitation Trends in Portsmouth

The chart displays monthly precipitation patterns in Portsmouth, 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 Portsmouth, May typically receives around 132 mm (5.2 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec9612111914713310410489110169117147
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Portsmouth

In Portsmouth in May humidity is 75%. With an average temperature of 12°C (55°F), this humidity feels like a damp blanket wrapping around you, making travel slightly uncomfortable as the chill magnifies the moisture in the air.

May Average Humidity in Portsmouth

This chart illustrates the average monthly humidity levels in Portsmouth, 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 Portsmouth is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%84%82%79%75%78%76%76%76%75%80%80%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Portsmouth

In Portsmouth in May, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Portsmouth.

Maximum UV Index Levels in Portsmouth for May

The chart shows the monthly maximum UV Index (UVI) for Portsmouth 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 Portsmouth typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3568910998642
Data source: Portsmouth 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 Portsmouth Compares to Other Months

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

This table compares monthly weather conditions in Portsmouth, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (35°F)95 mm (3.8 inches)84%moderate
February Weather2°C (36°F)121 mm (4.8 inches)84%moderate
March Weather3°C (39°F)119 mm (4.7 inches)82%high
April Weather8°C (46°F)147 mm (5.8 inches)79%very high
May Weather12°C (55°F)132 mm (5.2 inches)75%very high
June Weather18°C (64°F)104 mm (4.1 inches)78%very high
July Weather22°C (72°F)104 mm (4.1 inches)76%very high
August Weather22°C (73°F)89 mm (3.5 inches)76%very high
September Weather20°C (67°F)110 mm (4.3 inches)75%very high
October Weather15°C (60°F)169 mm (6.7 inches)75%high
November Weather9°C (48°F)117 mm (4.6 inches)80%moderate
December Weather4°C (39°F)147 mm (5.8 inches)80%low

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