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May Weather in South Portland, United States

Last updated: June 24, 2025

In May, the average temperature in South Portland, United States is a comfortable 11°C (52°F). Expect minimums of 2°C (36°F) and maximums reaching up to 24°C (76°F). During this month, you can anticipate 94 mm (3.7 in) of precipitation spread over approximately 10 days, with an average humidity of 72%.

May Temperature in South Portland

In May in South Portland, the average temperature is 11°C (52°F). The maximum can reach 24°C (76°F), while the minimum can drop as low as 2°C (36°F). This makes South Portland an ideal destination for travelers seeking mild weather and a variety of outdoor activities during this time of year.

May Weather in South Portland: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in South Portland, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In South Portland, May typically has an average temperature of 11°C (52°F), with highs reaching up to 24°C (76°F) and lows dropping to around 2°C (36°F).
JanFebMarAprMayJunJulAugSepOctNovDec282934435262686963544232
Data source: Temperature data for South Portland 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 South Portland

In South Portland in May, the precipitation amount is 94 mm (3.7 in) over a duration of 10 days.

May Precipitation Trends in South Portland

The chart displays monthly precipitation patterns in South Portland, 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 South Portland, May typically receives around 94 mm (3.7 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec971039114994801237577163130144
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in South Portland

In South Portland in May, humidity is 72%. With an average temperature of 11°C (52°F), this humidity feels like a damp chill that can make outdoor activities uncomfortable, often leaving travelers feeling slightly cold and clammy unless they are dressed in layers.

May Average Humidity in South Portland

This chart illustrates the average monthly humidity levels in South Portland, 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 South Portland is approximately 72%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%82%80%72%72%67%66%71%79%84%81%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in South Portland

In South Portland 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 South Portland.

Maximum UV Index Levels in South Portland for May

The chart shows the monthly maximum UV Index (UVI) for South Portland 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 South Portland typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2457910987532
Data source: South Portland 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 South Portland Compares to Other Months

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

This table compares monthly weather conditions in South Portland, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (28°F)97 mm (3.8 inches)86%low
February Weather-2°C (29°F)103 mm (4.1 inches)84%moderate
March Weather1°C (34°F)91 mm (3.6 inches)82%moderate
April Weather6°C (43°F)149 mm (5.9 inches)80%high
May Weather11°C (52°F)94 mm (3.7 inches)72%very high
June Weather17°C (62°F)80 mm (3.2 inches)72%very high
July Weather20°C (68°F)123 mm (4.9 inches)67%very high
August Weather20°C (69°F)75 mm (3.0 inches)66%very high
September Weather17°C (63°F)77 mm (3.0 inches)71%high
October Weather12°C (54°F)163 mm (6.4 inches)78%moderate
November Weather5°C (42°F)130 mm (5.1 inches)84%moderate
December Weather0°C (33°F)144 mm (5.7 inches)81%low

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