September weather forecastSouth Portland, ME
September
Weather in September
September introduces autumn to South Portland with noticeable changes in weather patterns. Taking a cue from August's end, temperatures begin to cool with the average high coming down to 66.4°F (19.1°C). The city starts its gradual transformation into the fall palette, replacing green leaves with shades of red, orange, and yellow. Extended sunshine hours during the day followed by slightly chilly evenings become typical. With the dipping temperature and humidity levels, air becomes crisp, marking a clear transition into fall's splendor.Temperature
In South Portland, the average high-temperature in September slightly decreases from an agreeable 72.3°F (22.4°C) in August to an enjoyable 66.4°F (19.1°C). An average nighttime temperature of 56.3°F (13.5°C) is witnessed throughout September.Humidity
In South Portland, the average relative humidity in September is 79%.Rainfall
The month with the least rainfall is September, when the rain falls for 10.2 days and typically collects 1.18" (30mm) of precipitation.Snowfall
May through September are months without snowfall in South Portland.Ocean temperature
In September, the average ocean temperature in South Portland is 60.4°F (15.8°C).Note: For most people, swimming in water at 60.4°F (15.8°C) is not a pleasurable experience. Breathing control gets harder as the water temperature descends from 69.8°F (21°C) to 59°F (15°C).
Daylight
In South Portland, the average length of the day in September is 12h and 29min.On the first day of the month, sunrise is at 6:05 am and sunset at 7:16 pm. On the last day of September, sunrise is at 6:38 am and sunset at 6:23 pm EDT.
Sunshine
In South Portland, the average sunshine in September is 8.7h.UV index
In South Portland, Maine, the average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for ordinary individuals.Note: In September, an average UV index of 4 transforms into the following instructions:
Guard yourself - Avoiding sunburn is suggested. The mid-day Sun emits the most powerful UV radiation, so seek shade and minimize exposure. During bright days, sunglasses that offer UVA and UVB defense are recommended.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
South Portland, ME
- Average high temperature in September: 66.4°F
The warmest month (with the highest average high temperature) is July (72.5°F).
The month with the lowest average high temperature is January (31.1°F).
- Average low temperature in September: 56.3°F
The month with the highest average low temperature is July (62.2°F).
The coldest month (with the lowest average low temperature) is January (20.7°F).
Average pressure in September
South Portland, ME
- Average pressure in September: 30.05"Hg
The months with the highest atmospheric pressure are September and November (30.05"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
South Portland, ME
- Average wind speed in September: 8.5mph
The windiest month (with the highest average wind speed) is January (12.5mph).
The calmest months (with the lowest average wind speed) are July and August (7.5mph).
Average humidity in September
South Portland, ME
- Average humidity in September: 79%
The months with the highest relative humidity are June and July (82%).
The month with the lowest relative humidity is November (74%).
Average rainfall in September
South Portland, ME
- Average rainfall in September: 1.18"
The wettest month (with the highest rainfall) is October (2.36").
The driest month (with the least rainfall) is September (1.18").
Average rainfall days in September
South Portland, ME
- Average rainfall days in September: 10.2 days
The month with the highest number of rainy days is July (14.7 days).
The month with the least rainy days is January (5.7 days).
Average snowfall in September
South Portland, ME
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.91").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
South Portland, ME
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (7.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average sea temperature in September
South Portland, ME
- Average sea temperature in September: 60.5°F
The best month for swimming (with the highest average sea temperature) is August (63.7°F).
The coldest month (with the lowest average sea temperature) is March (38°F).
Average daylight in September /
Average sunshine in September
South Portland, ME
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in September: 8h and 42min
The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 48min).
Average sunshine days in September
South Portland, ME
- Average sunshine days in September: 17.5 days
The month with the most sunshine days is November (19 days).
The month with the least sunshine days is July (13.8 days).
Average UV index in September
South Portland, ME
- Average UV index in September: 4
The months with the highest UV index are June, July and August (UV index 5).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
South Portland, ME
- Average cloud cover in September: 31
The month with the most cloud cover is March (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 29).
Average visibility in September
South Portland, ME
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
