Great Falls
Montana, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Great Falls, MT

A far view from on top of the vast Missouri River of the City of Lights, Great Falls, Montana, a dusk sky, mirror images in the water
A far view from on top of the vast Missouri River of the City of Lights, Great Falls, Montana, a dusk sky, mirror images in the water
September, the first month of the autumn, in Great Falls, is also an agreeable month, with temperature in the range of an average low of 42.1°F (5.6°C) and an average high of 70.3°F (21.3°C).

Temperature

In Great Falls, the average high-temperature decreases, from a moderately hot 82.2°F (27.9°C) in August, to a pleasant 70.3°F (21.3°C). In September, the average low-temperature is 42.1°F (5.6°C).

Rainfall

In Great Falls, it is raining for 7.8 days, with typically 1.4" (36.1mm) of accumulated precipitation. In Great Falls, during the entire year, the rain falls for 99.9 days and collects up to 14.8" (374.8mm) of precipitation.

Snowfall

Months with snowfall are January through June, August through December.

Daylight

The average length of the day is 12.5h.

Sunshine

In September, the average sunshine is 8.5h.

UV index

In September, the average daily maximum UV index in Great Falls is 5. A UV Index value of 3 to 5 symbolizes a medium health hazard from the exposure to the Sun's UV radiation for ordinary individuals.
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. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.

What is the temperature in September in Great Falls?

In Great Falls, Montana, in September, the average high-temperature is 70.3°F (21.3°C), and the average low-temperature is 42.1°F (5.6°C).

How many days does it rain in September in Great Falls?

In Great Falls, in September, it is raining for 7.8 days, with typically 1.4" (36.1mm) of accumulated precipitation.

How much does it snow in Great Falls in September?

In Great Falls, in September, during 0.8 snowfall days, 1.2" (30.5mm) of snow is typically accumulated.

How many hours of daylight does Great Falls have in September?

In September, the average length of the day in Great Falls is 12.5h.

How long on average sun shines in September in Great Falls?

In Great Falls, the average sunshine in September is 8.5h.

What is the UV index reading in September in Great Falls?

The average daily maximum UV index in September in Great Falls is 5. A UV Index value of 3 to 5 symbolizes a medium hazard to health from the exposure to the Sun's UV radiation.
Average temperature in September - Great Falls, MT
  • Average high temperature in September: 70.3°F

The warmest month (with the highest average high temperature) is July (83.4°F).
The month with the lowest average high temperature is December (34.6°F).

  • Average low temperature in September: 42°F

The month with the highest average low temperature is July (51.4°F).
Coldest months (with the lowest average low temperature) are January and December (14.9°F).

Average rainfall in September - Great Falls, MT
  • Average rainfall in September: 1.4"

The wettest month (with the highest rainfall) is June (2.5").
Driest months (with the lowest rainfall) are January and February (0.5").

Average rainfall days in September - Great Falls, MT
  • Average rainfall days in September: 7.8 days

Months with the highest number of rainy days are May and June (11.7 days).
The month with the lowest number of rainy days is October (6.6 days).

Average snowfall in September - Great Falls, MT
  • Average snowfall in September: 1.2"

The month with the highest snowfall is March (11.9").
The month with the lowest snowfall is July (0").

Average snowfall days in September - Great Falls, MT
  • Average snowfall days in September: 0.8 days

The month with the highest number of snowfall days is March (7.8 days).
The month with the lowest number of snowfall days is July (0 days).

Average daylight in September / Average sunshine in September - Great Falls, MT
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.9h).
The month with shortest days is December (Average daylight: 8.5h).

  • Average sunshine in September: 8.5h

The month with most sunshine is July (Average sunshine: 12.2h).
The month with least sunshine is December (Average sunshine: 3.4h).

Average UV index in September - Great Falls, MT
  • 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).