Juneau
Alaska, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Juneau, AK

Blooming fireweed in Juneau, Alaska, with snowy mountain peaks in the distance
Blooming fireweed in Juneau, Alaska, with snowy mountain peaks in the distance
The first month of the autumn, September, is still a chilly month in Juneau, Alaska, with average temperature varying between 44.4°F (6.9°C) and 48.2°F (9°C).

Temperature

In September, the average high-temperature slightly decreases, from a cool 54.1°F (12.3°C) in August, to a chilly 48.2°F (9°C). In September, the average low-temperature is 44.4°F (6.9°C).

Humidity

In Juneau, the average relative humidity in September is 90%.

Rainfall

In Juneau, Alaska, during 21.9 rainfall days, 8.27" (210mm) of precipitation is typically accumulated. In Juneau, during the entire year, the rain falls for 172.4 days and collects up to 85.87" (2181mm) of precipitation.

Snowfall

In Juneau snow does not fall in June through September.

Ocean temperature

In Juneau, Alaska, the average water temperature is 50.9°F (10.5°C).
Note: Swimming in 50.9°F (10.5°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.

Daylight

The average length of the day in September is 12.8h.

Sunshine

In September, the average sunshine in Juneau is 4.9h.

UV index

In September, the average daily maximum UV index in Juneau is 2. A UV Index of 2, and less, symbolizes a low health risk from unsafe exposure to the UV radiation for the ordinary person.
Note: The average daily UV index of 2 in September transform into the following instructions:
Extended sun exposure is not an issue for the majority. Children, infants, and fair-skinned individuals always need to be protected. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.

What is the temperature in September in Juneau?

In September, in Juneau, Alaska, the average high-temperature is 48.2°F (9°C), and the average low-temperature is 44.4°F (6.9°C).

What is the average humidity in September in Juneau?

In Juneau, the average relative humidity in September is 90%.

How many days does it rain in September in Juneau?

In Juneau, during September, the rain falls for 21.9 days and regularly aggregates up to 8.27" (210mm) of precipitation.

Does it snow in Juneau in September?

In Juneau, in September, it doesn't snow. In October, it regularly snows.

When it does not snow in Juneau?

In Juneau, Alaska, snow does not fall in June through September.

What is the water temperature in September in Juneau?

In Juneau, Alaska, the average seawater temperature in September is 50.9°F (10.5°C). Swimming in 50.9°F (10.5°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.

How many hours of daylight does Juneau have in September?

In Juneau, Alaska, the average length of the day in September is 12.8h.

How long on average sun shines in September in Juneau?

The average sunshine in September in Juneau, Alaska, is 4.9h.

What is the UV index intensity in September in Juneau?

In Juneau, the average daily maximum UV index in September is 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from unsafe exposure to the Sun's UV rays.
Average temperature in September - Juneau, AK
  • Average high temperature in September: 48.2°F

The warmest month (with the highest average high temperature) is July (55.8°F).
Months with the lowest average high temperature are January and December (25.7°F).

  • Average low temperature in September: 44.4°F

The month with the highest average low temperature is July (50°F).
The coldest month (with the lowest average low temperature) is January (23.7°F).

Average humidity in September - Juneau, AK
  • Average humidity in September: 90%

The month with the highest relative humidity is January (92%).
The month with the lowest relative humidity is May (86%).

Average rainfall in September - Juneau, AK
  • Average rainfall in September: 8.27"

The wettest month (with the highest rainfall) is October (9.88").
The driest month (with the lowest rainfall) is May (4.13").

Average rainfall days in September - Juneau, AK
  • Average rainfall days in September: 21.9 days

The month with the highest number of rainy days is September (21.9 days).
The month with the lowest number of rainy days is February (4.8 days).

Average snowfall in September - Juneau, AK
  • Average snowfall in September: 0"

The month with the highest snowfall is December (62.8").
Months with the lowest snowfall are June, July, August and September (0").

Average snowfall days in September - Juneau, AK
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (21.9 days).
Months with the lowest number of snowfall days are June, July, August and September (0 days).

Average sea temperature in September - Juneau, AK
  • Average sea temperature in September: 50.9°F

The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is March (40.3°F).

Average daylight in September / Average sunshine in September - Juneau, AK
  • Average daylight in September: 12.8h

The month with the longest days is June (Average daylight: 18.2h).
The month with shortest days is December (Average daylight: 6.5h).

  • Average sunshine in September: 4.9h

The month with most sunshine is June (Average sunshine: 6.4h).
The month with least sunshine is November (Average sunshine: 2.6h).

Average UV index in September - Juneau, AK
  • Average UV index in September: 2

Months with the highest UV index are May and July (UV index 3).
Months with the lowest UV index are January, April, October, November and December (UV index 1).