September weather forecast and climate
Simpson, MT

The first month of the autumn, September, is still a pleasant month in Simpson, Montana, with average temperature ranging between max 70.5°F (21.4°C) and min 52.5°F (11.4°C).

Temperature

In September, the average high-temperature decreases, from a moderately hot 81.3°F (27.4°C) in August, to an agreeable 70.5°F (21.4°C). In September, the average low-temperature is 52.5°F (11.4°C).

Humidity

The average relative humidity in September is 45%.

Rainfall

In Simpson, during September, the rain falls for 7.6 days and regularly aggregates up to 0.63" (16mm) of precipitation. In Simpson, Montana, during the entire year, the rain falls for 98.7 days and collects up to 8.23" (209mm) of precipitation.

Snowfall

January through May, September through December are months with snowfall in Simpson. September is the first month it typically snows in Simpson, Montana. Throughout September, in the average 0.2 snowfall days, it receives 0.51" (13mm) of snow. In Simpson, during the entire year, snow falls for 53.5 days, and aggregates up to 14.25" (362mm) of snow.

Daylight

In Simpson, the average length of the day is 12.6h.

Sunshine

The average sunshine in Simpson is 10.1h.

UV index

The average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from unsafe exposure to the UV radiation for the average person.
Note: The daily maximum UV index of 4 interpret into the following advice:
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 Simpson?

In September, in Simpson, the average high-temperature is 70.5°F (21.4°C), and the average low-temperature is 52.5°F (11.4°C).

What is the average humidity in September in Simpson?

In September, the average relative humidity in Simpson is 45%.

How much does it rain in Simpson in September?

In September, in Simpson, Montana, the rain falls for 7.6 days. Throughout September, 0.63" (16mm) of precipitation is accumulated.

When does it start snowing in Simpson?

September is the first month it typically snows in Simpson. Throughout September, in the average 0.2 snowfall days, it receives 0.51" (13mm) of snow.

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

The average length of the day in September in Simpson, Montana, is 12.6h.

How long on average sun shines in September in Simpson?

The average sunshine in September in Simpson, Montana, is 10.1h.

What is the UV index reading in September in Simpson?

In Simpson, Montana, the average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate vulnerability from the exposure to the Sun's UV radiation.
Average temperature in September - Simpson, MT
  • Average high temperature in September: 70.5°F

The warmest month (with the highest average high temperature) is July (82.8°F).
Months with the lowest average high temperature are January and December (27.1°F).

  • Average low temperature in September: 52.5°F

The month with the highest average low temperature is August (61.3°F).
The coldest month (with the lowest average low temperature) is February (13.5°F).

Average pressure in September - Simpson, MT
  • Average pressure in September: 29.93"

Months with the highest atmospheric pressure are January and February (30.12").
The month with the lowest atmospheric pressure is June (29.84").

Average wind speed in September - Simpson, MT
  • Average wind speed in September: 9mph

The windiest month (with the highest average wind speed) is April (10.6mph).
The calmest month (with the lowest average wind speed) is August (8.5mph).

Average humidity in September - Simpson, MT
  • Average humidity in September: 45%

The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is August (40%).

Average rainfall in September - Simpson, MT
  • Average rainfall in September: 0.63"

The wettest month (with the highest rainfall) is June (1.5").
The driest month (with the least rainfall) is December (0.31").

Average rainfall days in September - Simpson, MT
  • Average rainfall days in September: 7.6 days

The month with the highest number of rainy days is May (13.8 days).
The month with the least rainy days is February (4 days).

Average snowfall in September - Simpson, MT
  • Average snowfall in September: 0.51"

The month with the highest snowfall is February (2.72").
Months with the least snowfall are June, July and August (0").

Average snowfall days in September - Simpson, MT
  • Average snowfall days in September: 0.2 days

The month with the highest number of snowfall days is February (11 days).
Months with the least snowfall days are June, July and August (0 days).

Average daylight in September / Average sunshine in September - Simpson, 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: 10.1h

The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is February (Average sunshine: 5.3h).

Average sunshine days in September - Simpson, MT
  • Average sunshine days in September: 20.3 days

The month with the most sunshine days is September (20.3 days).
The month with the least sunshine days is April (12.8 days).

Average UV index in September - Simpson, 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 - Simpson, MT
  • Average cloud cover in September: 22

The month with the most cloud cover is February (Cloud cover 46).
Months with the least cloud cover are July and August (Cloud cover 16).

Average visibility in September - Simpson, MT
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).