September weather forecastPortland, ME
September
Weather in September
With September, the city of Portland starts transitioning from summer to fall. It experiences temperatures ranging from 56.3°F (13.5°C) to 66.4°F (19.1°C). The city embarks on the journey of seeing the leaves change their clothes from green to brown. A crisp hint of autumn can be felt in the air, bringing a pleasant contrast to the preceding hot months. Visitors can enjoy the first tastes of fall during the annual Harvest on the Harbor food festival.Temperature
September's arrival in Portland aligns with a minor decrease in average high-temperatures, from August's pleasant 72.3°F (22.4°C) to a refreshing 66.4°F (19.1°C). In Portland, in September, the average low-temperature is a moderate 56.3°F (13.5°C).Humidity
In Portland, the average relative humidity in September is 79%.Rainfall
The month with the least rainfall in Portland 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 Portland.Ocean temperature
In Portland, in September, the average water temperature is 60.4°F (15.8°C).Note: Swimming is not an enjoyable activity for the majority when the water is at 60.4°F (15.8°C). The difficulty of controlling breathing increases as the temperature dips from 69.8°F (21°C) to 59°F (15°C).
Daylight
In Portland, the average length of the day in September is 12h and 29min.On the first day of September, sunrise is at 6:05 am and sunset at 7:16 pm. On the last day of the month, sunrise is at 6:38 am and sunset at 6:23 pm EDT.
Sunshine
In Portland, the average sunshine in September is 8.7h.UV index
The average daily maximum UV index in September in Portland is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for ordinary individuals.Note: The average daily UV index of 4 in September transforms into the following instructions:
Make use of precautions - Suggestions to resist sunburn are communicated. The Sun's radiation is especially intense around midday; try to stay in shade during this period. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
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
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
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
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
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
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
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
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
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
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
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
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
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
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).
