Portland, Maine weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Poor
Best time to visit: July – August
What is the weather like in Portland, Maine in September?
In September, Portland, Maine is mild: daytime highs average 20 °C, and nights cool down to about 14 °C. The sea averages 15.9 °C – swimming is only for the hardy. The sun shines for around 7 hours a day. Rain falls on about 8 days, adding up to 81 mm. All in all, September is not an ideal month for a holiday in Portland, Maine.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 58 | 33 | 20 |
| Day | 24° | 20° | 14° |
| Night | 18° | 14° | 9° |
| Sea | 18° | 16° | 13° |
| Sun | 8 h | 7 h | 5 h |
| Rain days | 9 | 8 | 10 |
More details for September
- Daylight
- 12 h 35 min06:19 – 18:54
- UV index
- 5 · moderateclear sky, noon (estimate)All months
- Muggy days
- 3 daysdew point 18 °C or moreAll months
- Wind
- 16 km/haverage daily peakAll months
- Cloud cover
- 52 %on averageAll months
- Hot days
- 0 days30 °C or moreAll months
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 35 %18 %
- Seaweight 25 %0 %
- Sunshineweight 20 %60 %
- Few rainy daysweight 20 %71 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Sunscreen
- A jumper for the evenings
- Rain jacket or umbrella
Portland, Maine in September: quick answers
Is Portland, Maine hot in September?
No. In September, Portland, Maine is mild: daytime highs average 20 °C and nights drop to about 14 °C.
Can you swim in Portland, Maine in September?
Only if you don't mind cold water: in September the sea averages just 15.9 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Portland, Maine in September?
Rain falls on about 8 days, adding up to 81 mm.
Portland, Maine month by month
The whole year in Portland, MaineAll destinations: USAWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences