Portland weather in September 2025

Expect 21°C daytime maximum temperatures in the shade with on average 7 hours of sunshine per day in Portland in September. Check more long-term weather averages for Portland in September before you book your next holiday to Maine in 2025/2026.

  • 21°C maximum daytime temperature in September in Portland21
    21°C max day temperature
  • 7 hours of sunshine per day
  • 9 days with some rainfall in September in Portland9
    9 days with some rainfall
  • 10°C minimum night-time temperature in September in Portland10
    10°C min night temperature
  • 12 hours of daylight per day in September in Portland12
    12 hours of daylight per day
  • No heat & humidity in September in Portland0
    No heat & humidity
  • 81 mm monthly rainfall in September in Portland81
    81 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Portland5
    5 (Moderate) UV index
  • 15°C sea temperature in September in Portland15
    15°C sea temperature

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The September weather guide for Maine (Portland) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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More about the USA

How hot is it in Portland in September?

Daytime temperatures usually reach 21°C in Portland in September, falling to 10°C at night.

How sunny is it in Portland in September?

There are normally 7 hours of bright sunshine each day in Portland in September - that's 59% of daylight hours.

How warm is the sea around Portland in September?

The average sea temperature around Portland in September is 15°C.

Does it rain in Portland in September?

There are usually 9 days with some rain in Portland in September and the average monthly rainfall is 81mm.

What is the chance of a hurricane in Portland in September?

On average less than 1 day in September in Portland is likely to be affected by the passage of one or more tropical storms.

Portland September sunrise & sunset times

Browse the sunrise and sunset times for Portland in September 2025. Select a month to view Portland sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:05 18:16
Monday, 15th September 2025 05:21 17:51
Tuesday, 30th September 2025 05:38 17:23

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