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September Weather in South Portland, United States

Last updated: June 24, 2025

In South Portland, United States, the average temperature in September hovers around 17°C (63°F), providing a pleasant climate for outdoor activities. Expect temperatures to range from a cool 8°C (46°F) at night to a warm 26°C (79°F) during the day. With an average precipitation of 77 mm (3.0 in) over 8 days, you may encounter some rain, so pack accordingly! Additionally, the average humidity stands at 71%, giving a hint of warmth in the air. Enjoy your time in this charming locale!

September Temperature in South Portland

In September in South Portland, the average temperature is 17°C (63°F). Maximums can reach 26°C (79°F), and minimums can be as low as 8°C (46°F). This mild climate makes South Portland an ideal destination for travelers seeking comfortable weather for outdoor activities.

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

The chart illustrates September 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, September typically has an average temperature of 17°C (63°F), with highs reaching up to 26°C (79°F) and lows dropping to around 8°C (46°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.

September Precipitation in South Portland

In South Portland in September, the precipitation amount is 77 mm (3.0 in) distributed over 8 days.

September Precipitation Trends in South Portland

The chart displays monthly precipitation patterns in South Portland, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In South Portland, September typically receives around 77 mm (3.0 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec971039114994801237577163130144
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in South Portland

In South Portland in September, humidity is 71%. With an average temperature of 17°C (63°F), this humidity feels like a warm embrace, making outdoor activities enjoyable yet a bit sticky, so travelers should stay hydrated and take breaks in the shade.

September Average Humidity in South Portland

This chart illustrates the average monthly humidity levels in South Portland, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in South Portland is approximately 71%, 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 September generated using information from the Copernicus Climate Change Service.

September UV Index in South Portland

In South Portland in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in South Portland.

Maximum UV Index Levels in South Portland for September

The chart shows the monthly maximum UV Index (UVI) for South Portland in September, 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 September, the maximum UV index in South Portland typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2457910987532
Data source: South Portland September 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 September 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 September’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 September’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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