September weather forecast and climate
Sweet Grass, MT

The first month of the autumn, September, is still a comfortable month in Sweet Grass, Montana, with average temperature varying between 48.4°F (9.1°C) and 67.6°F (19.8°C).

Temperature

In September, the average high-temperature drops, from a moderately hot 78.1°F (25.6°C) in August, to a comfortable 67.6°F (19.8°C). In Sweet Grass, the average low-temperature is 48.4°F (9.1°C).

Humidity

In Sweet Grass, Montana, the average relative humidity in September is 49%.

Rainfall

In Sweet Grass, Montana, during 6.2 rainfall days, 0.71" (18mm) of precipitation is typically accumulated. In Sweet Grass, during the entire year, the rain falls for 70.4 days and collects up to 8.46" (215mm) of precipitation.

Snowfall

January through May, September through December are months with snowfall. September is the first month it typically snows. Throughout September, in the average 0.8 snowfall days, it receives 0.51" (13mm) of snow. In Sweet Grass, during the entire year, snow falls for 54.3 days, and aggregates up to 19.49" (495mm) of snow.

Daylight

In Sweet Grass, the average length of the day in September is 12.6h.

Sunshine

In Sweet Grass, the average sunshine in September is 9.6h.

UV index

The average daily maximum UV index in Sweet Grass is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from unprotected exposure to the Sun's UV rays for the average person.
Note: The daily maximum UV index of 4 interpret into the following advice:
Take precautions - Protection against sunburn is recommended. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.

What is the temperature in September in Sweet Grass?

The average high-temperature, in September, is 67.6°F (19.8°C), while the average low-temperature is 48.4°F (9.1°C).

What is the average humidity in September in Sweet Grass?

In Sweet Grass, the average relative humidity in September is 49%.

How many days does it rain in September in Sweet Grass?

In September, the rain falls for 6.2 days. Throughout September, 0.71" (18mm) of precipitation is accumulated.

When does it start snowing in Sweet Grass?

September is the first month it typically snows in Sweet Grass, Montana. Throughout September, in the average 0.8 snowfall days, it receives 0.51" (13mm) of snow.

What is the average length of the day in September in Sweet Grass?

In September, the average length of the day in Sweet Grass, Montana, is 12.6h.

How many hours of sunshine does Sweet Grass have in September?

In September, the average sunshine in Sweet Grass is 9.6h.

How high is the UV index in September in Sweet Grass?

In September, the average daily maximum UV index in Sweet Grass, Montana, is 4. A UV Index reading of 3 to 5 represents a moderate vulnerability from the exposure to the Sun's UV rays.
Average temperature in September - Sweet Grass, MT
  • Average high temperature in September: 19.8°C

The warmest month (with the highest average high temperature) is July (26°C).
The month with the lowest average high temperature is December (-2.7°C).

  • Average low temperature in September: 9.1°C

The month with the highest average low temperature is August (12.9°C).
The coldest month (with the lowest average low temperature) is December (-9.3°C).

Average pressure in September - Sweet Grass, MT
  • Average pressure in September: 1014.2mbar

The month with the highest atmospheric pressure is January (1020.3mbar).
The month with the lowest atmospheric pressure is June (1011.5mbar).

Average wind speed in September - Sweet Grass, MT
  • Average wind speed in September: 15.3km/h

The windiest month (with the highest average wind speed) is January (19km/h).
The calmest month (with the lowest average wind speed) is August (14.1km/h).

Average humidity in September - Sweet Grass, MT
  • Average humidity in September: 49%

The month with the highest relative humidity is January (79%).
The month with the lowest relative humidity is August (43%).

Average rainfall in September - Sweet Grass, MT
  • Average rainfall in September: 18mm

The wettest month (with the highest rainfall) is June (45mm).
The driest month (with the least rainfall) is July (8mm).

Average rainfall days in September - Sweet Grass, MT
  • Average rainfall days in September: 6.2 days

The month with the highest number of rainy days is May (10.4 days).
The month with the least rainy days is November (2.6 days).

Average snowfall in September - Sweet Grass, MT
  • Average snowfall in September: 13mm

The month with the highest snowfall is February (91mm).
Months with the least snowfall are June, July and August (0mm).

Average snowfall days in September - Sweet Grass, MT
  • Average snowfall days in September: 0.8 days

The month with the highest number of snowfall days is December (10.2 days).
Months with the least snowfall days are July and August (0 days).

Average daylight in September / Average sunshine in September - Sweet Grass, MT
  • Average daylight in September: 12.6h

The month with the longest days is June (Average daylight: 16.1h).
The month with the shortest days is December (Average daylight: 8.3h).

  • Average sunshine in September: 9.6h

The month with the most sunshine is July (Average sunshine: 12h).
Months with the least sunshine are January and December (Average sunshine: 5.6).

Average sunshine days in September - Sweet Grass, MT
  • Average sunshine days in September: 22.4 days

The month with the most sunshine days is July (23.5 days).
The month with the least sunshine days is April (17.4 days).

Average UV index in September - Sweet Grass, MT
  • Average UV index in September: 4

The month with the highest UV index is July (UV index 6).
Months with the lowest UV index are January, February, March, October, November and December (UV index 2).

Average cloud cover in September - Sweet Grass, MT
  • Average cloud cover in September: 23

The month with the most cloud cover is February (Cloud cover 43).
The month with the least cloud cover is July (Cloud cover 15).

Average visibility in September - Sweet Grass, MT
  • Average visibility in September: 10km

Months with the highest visibility are May, June, July, August, September and October (10km).
Months with the lowest visibility are January, February, March, April, November and December (9km).