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

September weather forecast and climate
Helena, MT

The State Capital building of Montana in Helena city, set on a beautiful natural park
The State Capital building of Montana in Helena city, set on a beautiful natural park
The first month of the autumn, September, is still a pleasant month in Helena, Montana, with average temperature ranging between max 72.7°F (22.6°C) and min 43.2°F (6.2°C).

Temperature

In Helena, the average high-temperature in September drops, from a moderately hot 84.6°F (29.2°C) in August, to an agreeable 72.7°F (22.6°C). The average low-temperature, is 43.2°F (6.2°C).

Humidity

In Helena, the average relative humidity is 54.5%.

Rainfall

In Helena, during September, the rain falls for 6.1 days and regularly aggregates up to 1.1" (27.9mm) of precipitation. In Helena, during the entire year, the rain falls for 91.6 days and collects up to 11.2" (284.9mm) of precipitation.

Snowfall

Months with snowfall in Helena are January through May, August through December. In Helena, during 0.7 snowfall days, 1.3" (33mm) of snow is typically accumulated. Throughout the year, in Helena, Montana, there are 32.8 snowfall days, and 38.1" (967.8mm) of snow is accumulated.

Daylight

The average length of the day in Helena is 12.5h.

Sunshine

In September, the average sunshine in Helena, Montana, is 8.5h.

UV index

The average daily maximum UV index in Helena, Montana, is 5. A UV Index estimate 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 5 interpret into the following advice:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. 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 Helena?

In Helena, in September, the average high-temperature is 72.7°F (22.6°C), and the average low-temperature is 43.2°F (6.2°C).

What is the average humidity in September in Helena?

In Helena, the average relative humidity in September is 54.5%.

How many days does it rain in September in Helena?

In Helena, Montana, in September, it is raining for 6.1 days, with typically 1.1" (27.9mm) of accumulated precipitation.

How much does it snow in Helena in September?

In September, in Helena, it is snowing for 0.7 days. Throughout September, 1.3" (33mm) of snow is accumulated.

How many hours of daylight does Helena have in September?

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

How long on average sun shines in September in Helena?

In September, the average sunshine in Helena, Montana, is 8.5h.

What is the UV index reading in September in Helena?

The average daily maximum UV index in September in Helena is 5. A UV Index reading of 3 to 5 represents a moderate health threat from unsafe exposure to the Sun's UV rays.
Average temperature in September - Helena, MT
  • Average high temperature in September: 72.6°F

The warmest month (with the highest average high temperature) is July (85.7°F).
The month with the lowest average high temperature is December (31.7°F).

  • Average low temperature in September: 43.1°F

The month with the highest average low temperature is July (54.3°F).
The coldest month (with the lowest average low temperature) is December (11.9°F).

Average humidity in September - Helena, MT
  • Average humidity in September: 54.5%

The month with the highest relative humidity is December (68.1%).
The month with the lowest relative humidity is July (46.4%).

Average rainfall in September - Helena, MT
  • Average rainfall in September: 1.1"

The wettest month (with the highest rainfall) is June (2.1").
The driest month (with the lowest rainfall) is February (0.3").

Average rainfall days in September - Helena, MT
  • Average rainfall days in September: 6.1 days

The month with the highest number of rainy days is June (11.2 days).
The month with the lowest number of rainy days is February (5.9 days).

Average snowfall in September - Helena, MT
  • Average snowfall in September: 1.3"

The month with the highest snowfall is December (7.3").
Months with the lowest snowfall are June and July (0").

Average snowfall days in September - Helena, MT
  • Average snowfall days in September: 0.7 days

The month with the highest number of snowfall days is December (6 days).
The month with the lowest number of snowfall days is July (0 days).

Average daylight in September / Average sunshine in September - Helena, 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: 8.6h).

  • Average sunshine in September: 8.5h

The month with most sunshine is July (Average sunshine: 11.9h).
The month with least sunshine is December (Average sunshine: 3.2h).

Average UV index in September - Helena, MT
  • Average UV index in September: 5

The month with the highest UV index is July (UV index 9).
Months with the lowest UV index are January, November and December (UV index 1).