Green Bay
Wisconsin, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Green Bay, WI

An aerial panorama of the sun setting over Green Bay in Wisconsin
An aerial panorama of the sun setting over Green Bay in Wisconsin
September, the first month of the autumn, in Green Bay, is still a pleasant month, with temperature in the range of an average low of 48.6°F (9.2°C) and an average high of 70°F (21.1°C).

Temperature

In September, the average high-temperature slightly decreases, from a moderately hot 77.7°F (25.4°C) in August, to an agreeable 70°F (21.1°C). In September, in Green Bay, the average low-temperature is 48.6°F (9.2°C).

Humidity

In September, the average relative humidity is 76.5%.

Rainfall

In Green Bay, Wisconsin, in September, it is raining for 9.7 days, with typically 3" (77.2mm) of accumulated precipitation. In Green Bay, during the entire year, the rain falls for 123 days and collects up to 29.5" (749.9mm) of precipitation.

Snowfall

June through September are months without snowfall.

Ocean temperature

In September, the average ocean temperature is 63.9°F (17.7°C).
Note: For most, swimming in 63.9°F (17.7°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).

Daylight

In September, the average length of the day in Green Bay is 12.5h.

Sunshine

In September, the average sunshine is 6.8h.

UV index

In September, the average daily maximum UV index is 5. A UV Index of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV radiation for the ordinary person.
Note: In September, the average maximum UV index of 5 translate into the following recommendations:
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. 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 Green Bay?

In Green Bay, in September, the average high-temperature is 70°F (21.1°C), and the average low-temperature is 48.6°F (9.2°C).

What is the average humidity in September in Green Bay?

In Green Bay, Wisconsin, the average relative humidity in September is 76.5%.

How much does it rain in Green Bay in September?

In Green Bay, Wisconsin, during September, the rain falls for 9.7 days and regularly aggregates up to 3" (77.2mm) of precipitation.

Does it snow in Green Bay in September?

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

When it does not snow in Green Bay?

June through September are months without snowfall.

What is the ocean temperature in September in Green Bay?

In Green Bay, in September, the average water temperature is 63.9°F (17.7°C). For swimming, a surface water temperature of 63.9°F (17.7°C) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 69.8°F (21°C).

How many hours of daylight does Green Bay have in September?

The average length of the day in September in Green Bay, Wisconsin, is 12.5h.

How many hours of sunshine does Green Bay have in September?

The average sunshine in September in Green Bay, Wisconsin, is 6.8h.

How high is the UV index in September in Green Bay?

In Green Bay, the average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate vulnerability from the exposure to the Sun's UV radiation.
Average temperature in September - Green Bay, WI
  • Average high temperature in September: 69.9°F

The warmest month (with the highest average high temperature) is July (79.8°F).
The month with the lowest average high temperature is January (24.3°F).

  • Average low temperature in September: 48.5°F

The month with the highest average low temperature is July (58.4°F).
The coldest month (with the lowest average low temperature) is January (9°F).

Average humidity in September - Green Bay, WI
  • Average humidity in September: 76.5%

The month with the highest relative humidity is December (77.3%).
The month with the lowest relative humidity is May (65.9%).

Average rainfall in September - Green Bay, WI
  • Average rainfall in September: 3"

The wettest month (with the highest rainfall) is June (3.9").
Driest months (with the lowest rainfall) are January and February (1.1").

Average rainfall days in September - Green Bay, WI
  • Average rainfall days in September: 9.7 days

The month with the highest number of rainy days is May (11.4 days).
The month with the lowest number of rainy days is February (8.4 days).

Average snowfall in September - Green Bay, WI
  • Average snowfall in September: 0"

The month with the highest snowfall is December (13.1").
Months with the lowest snowfall are June, July, August and September (0").

Average snowfall days in September - Green Bay, WI
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (9.6 days).
Months with the lowest number of snowfall days are June, July, August and September (0 days).

Average sea temperature in September - Green Bay, WI
  • Average sea temperature in September: 63.8°F

The best month for swimming (with the highest average sea temperature) is August (67.6°F).
The coldest month (with the lowest average sea temperature) is February (36.1°F).

Average daylight in September / Average sunshine in September - Green Bay, WI
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.5h).
The month with shortest days is December (Average daylight: 8.9h).

  • Average sunshine in September: 6.8h

Months with most sunshine are June and July (Average sunshine: 10.1h).
Months with least sunshine are November and December (Average sunshine: 3.6).

Average UV index in September - Green Bay, WI
  • 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 and December (UV index 1).