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

September weather forecast and climate
Roundup, MT

September, the first month of the autumn, in Roundup, is still a warm month, with average temperature fluctuating between 43.7°F (6.5°C) and 76.5°F (24.7°C).


In Roundup, Montana, the average high-temperature decreases, from a hot 88.2°F (31.2°C) in August, to a warm 76.5°F (24.7°C). The average low-temperature, in Roundup, is 43.7°F (6.5°C).


During September, Roundup regularly aggregates up to 1.2" (30.2mm) of precipitation. During the entire year, Roundup aggregates up to 13.5" (343.1mm) of precipitation.


June through September are months without snowfall.


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

What is the temperature in September in Roundup?

The average high-temperature, in September, in Roundup, is 76.5°F (24.7°C), while the average low-temperature is 43.7°F (6.5°C).

How much does it rain in Roundup in September?

In Roundup, Montana, in September, 1.2" (30.2mm) of precipitation is typically accumulated.

Does it snow in Roundup in September?

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

When it does not snow in Roundup?

In Roundup snow does not fall in June through September.

How many hours of daylight does Roundup have in September?

The average length of the day in September in Roundup is 12.5h.
Average temperature in September - Roundup, MT
  • Average high temperature in September: 76.4°F

The warmest month (with the highest average high temperature) is July (88.9°F).
The month with the lowest average high temperature is December (37.8°F).

  • Average low temperature in September: 43.7°F

The month with the highest average low temperature is July (55.5°F).
The coldest month (with the lowest average low temperature) is December (15.2°F).

Average rainfall in September - Roundup, MT
  • Average rainfall in September: 1.2"

The wettest month (with the highest rainfall) is June (2.6").
Driest months (with the lowest rainfall) are January and February (0.3").

Average snowfall in September - Roundup, MT
  • Average snowfall in September: 0"

Months with the highest snowfall are January and December (5.3").
Months with the lowest snowfall are June, July, August and September (0").

Average daylight in September - Roundup, MT
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.8h).
The month with shortest days is December (Average daylight: 8.7h).