Duluth
Minnesota, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Duluth, MN

A dusk view of bright neon lights in Duluth, Minnesota, and a clear view of the lit Aerial Lift Bridge, and two long piers with lighthouses at the ends
A dusk view of bright neon lights in Duluth, Minnesota, and a clear view of the lit Aerial Lift Bridge, and two long piers with lighthouses at the ends
September, the first month of the autumn, in Duluth, is also an enjoyable month, with average temperature ranging between max 64.9°F (18.3°C) and min 46°F (7.8°C).

Temperature

In Duluth, Minnesota, the average high-temperature in September decreases, from a warm 74.3°F (23.5°C) in August, to an enjoyable 64.9°F (18.3°C). The average low-temperature, in Duluth, Minnesota, is 46°F (7.8°C).

Humidity

In September, the average relative humidity is 75.7%.

Rainfall

In September, the rain falls for 12.3 days. Throughout September, 4.1" (104.4mm) of precipitation is accumulated. In Duluth, during the entire year, the rain falls for 131.4 days and collects up to 31" (786.3mm) of precipitation.

Snowfall

Months with snowfall in Duluth are January through May, September through December.

Ocean temperature

In September, the average ocean temperature in Duluth, Minnesota, is 57.2°F (14°C). At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.

Daylight

The average length of the day in September is 12.5h.

Sunshine

In September, the average sunshine is 6.5h.

UV index

In September, the average daily maximum UV index is 5. A UV Index reading of 3 to 5 represents a moderate health risk from the exposure to the Sun's UV rays for the ordinary person.
The average daily UV index of 5 in September transform into the following instructions:
Take precautions - Protection against sun damage is advised. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.

What is the temperature in September in Duluth?

In Duluth, in September, the average high-temperature is 64.9°F (18.3°C), and the average low-temperature is 46°F (7.8°C).

What is the average humidity in September in Duluth?

The average relative humidity in September in Duluth, Minnesota, is 75.7%.

How much does it rain in Duluth in September?

In Duluth, Minnesota, in September, it is raining for 12.3 days, with typically 4.1" (104.4mm) of accumulated precipitation.

When does it start to snow in Duluth?

September is the first month it typically snows. Throughout September, in the average 0.1 snowfall days, it receives 0.1" (2.5mm) of snow.

How cold is the water in September in Duluth?

In Duluth, Minnesota, the average seawater temperature in September is 57.2°F (14°C). Swimming in 57.2°F (14°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

What is the average length of the day in September in Duluth?

The average length of the day in September is 12.5h.

How many hours of sunshine does Duluth have in September?

In Duluth, the average sunshine in September is 6.5h.

What is the UV index intensity in September in Duluth?

In Duluth, the average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a medium hazard to health from unprotected exposure to the UV radiation.
Average temperature in September - Duluth, MN
  • Average high temperature in September: 65°F

The warmest month (with the highest average high temperature) is July (76.3°F).
The month with the lowest average high temperature is January (18.9°F).

  • Average low temperature in September: 46.1°F

The month with the highest average low temperature is July (55.4°F).
The coldest month (with the lowest average low temperature) is January (1.5°F).

Average humidity in September - Duluth, MN
  • Average humidity in September: 75.7%

The month with the highest relative humidity is December (76.3%).
The month with the lowest relative humidity is May (62.7%).

Average rainfall in September - Duluth, MN
  • Average rainfall in September: 4.1"

The wettest month (with the highest rainfall) is June (4.2").
The driest month (with the lowest rainfall) is February (0.8").

Average rainfall days in September - Duluth, MN
  • Average rainfall days in September: 12.3 days

The month with the highest number of rainy days is June (12.6 days).
The month with the lowest number of rainy days is February (8.5 days).

Average snowfall in September - Duluth, MN
  • Average snowfall in September: 0.1"

The month with the highest snowfall is January (19.4").
Months with the lowest snowfall are June, July and August (0").

Average snowfall days in September - Duluth, MN
  • Average snowfall days in September: 0.1 days

The month with the highest number of snowfall days is January (12.9 days).
Months with the lowest number of snowfall days are June, July and August (0 days).

Average sea temperature in September - Duluth, MN
  • Average sea temperature in September: 57°F

The best month for swimming (with the highest average sea temperature) is August (61°F).
Coldest months (with the lowest average sea temperature) are January, February, March and April (36°F).

Average daylight in September / Average sunshine in September - Duluth, MN
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.8h).
The month with shortest days is December (Average daylight: 8.6h).

  • Average sunshine in September: 6.5h

The month with most sunshine is July (Average sunshine: 9.9h).
Months with least sunshine are November and December (Average sunshine: 3.3).

Average UV index in September - Duluth, MN
  • Average UV index in September: 5

Months with the highest UV index are June and July (UV index 8).
Months with the lowest UV index are January, November and December (UV index 1).