September weather forecast
Heron, MT

Weather in September

September, the first month of the autumn, in Heron, is still a comfortable month, with average temperature varying between 41.7°F (5.4°C) and 67.8°F (19.9°C).

Temperature

In September, the average high-temperature decreases, from a warm 78.3°F (25.7°C) in August, to a comfortable 67.8°F (19.9°C). In Heron, the average low-temperature is 41.7°F (5.4°C).

Humidity

The average relative humidity in Heron is 63%.

Rainfall

In Heron, during September, the rain falls for 10.7 days and regularly aggregates up to 1.14" (29mm) of precipitation. In Heron, during the entire year, the rain falls for 161.9 days and collects up to 27.48" (698mm) of precipitation.

Snowfall

Months with snowfall in Heron are January through May, September through December. September is the first month it typically snows in Heron, Montana. Throughout September, in the average 0.3 snowfall days, it receives 0.28" (7mm) of snow. Throughout the year, in Heron, there are 80.8 snowfall days, and 60" (1524mm) of snow is accumulated.

Daylight

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

Sunshine

In September, the average sunshine is 9.5h.

UV index

In Heron, Montana, the average daily maximum UV index is 3. A UV Index value of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV radiation for average individuals.
Note: In September, the average maximum UV index of 3 translate into the following recommendations:
Take precautions - Protection against the skin and eye damage is obliged. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
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FAQ

What is the average humidity in September in Heron?

The average relative humidity in September in Heron, Montana, is 63%.

How many days does it rain in September in Heron?

In September, in Heron, Montana, the rain falls for 10.7 days. Throughout September, 1.14" (29mm) of precipitation is accumulated.

When does it start snowing in Heron?

September is the first month it typically snows in Heron. Throughout September, in the average 0.3 snowfall days, it receives 0.28" (7mm) of snow.

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

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

How long on average sun shines in September in Heron?

In Heron, the average sunshine in September is 9.5h.

What is the UV index intensity in September in Heron?

In September, the average daily maximum UV index is 3. A UV Index reading of 3 to 5 represents a medium health risk from unprotected exposure to the UV radiation.

Average temperature in September
Heron, MT

Average temperature in September - Heron, MT
  • Average high temperature in September: 67.8°F

The warmest month (with the highest average high temperature) is August (78.3°F).
The month with the lowest average high temperature is December (29.3°F).

  • Average low temperature in September: 41.7°F

The month with the highest average low temperature is August (49.1°F).
The coldest month (with the lowest average low temperature) is December (18.7°F).

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Average pressure in September
Heron, MT

Average pressure in September - Heron, MT
  • Average pressure in September: 29.97"

The month with the highest atmospheric pressure is January (30.19").
Months with the lowest atmospheric pressure are June and August (29.92").

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Average wind speed in September
Heron, MT

Average wind speed in September - Heron, MT
  • Average wind speed in September: 3.9mph

The windiest month (with the highest average wind speed) is April (4.5mph).
The calmest month (with the lowest average wind speed) is December (3.5mph).

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Average humidity in September
Heron, MT

Average humidity in September - Heron, MT
  • Average humidity in September: 63%

The month with the highest relative humidity is January (94%).
The month with the lowest relative humidity is August (52%).

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Average rainfall in September
Heron, MT

Average rainfall in September - Heron, MT
  • Average rainfall in September: 1.14"

The wettest month (with the highest rainfall) is December (3.66").
The driest month (with the least rainfall) is August (0.55").

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Average rainfall days in September
Heron, MT

Average rainfall days in September - Heron, MT
  • Average rainfall days in September: 10.7 days

The month with the highest number of rainy days is April (19.3 days).
The month with the least rainy days is August (6.9 days).

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Average snowfall in September
Heron, MT

Average snowfall in September - Heron, MT
  • Average snowfall in September: 0.28"

The month with the highest snowfall is January (15.87").
Months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Heron, MT

Average snowfall days in September - Heron, MT
  • Average snowfall days in September: 0.3 days

The month with the highest number of snowfall days is December (19.5 days).
Months with the least snowfall days are June, July and August (0 days).

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Average daylight in September /
Average sunshine in September
Heron, MT

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

The month with the longest days is June (Average daylight: 16h).
The month with the shortest days is December (Average daylight: 8.5h).

  • Average sunshine in September: 9.5h

The month with the most sunshine is August (Average sunshine: 11.8h).
The month with the least sunshine is January (Average sunshine: 3.2h).

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Average sunshine days in September
Heron, MT

Average sunshine days in September - Heron, MT
  • Average sunshine days in September: 17.5 days

The month with the most sunshine days is July (20.9 days).
The month with the least sunshine days is March (7.1 days).

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Average UV index in September
Heron, MT

Average UV index in September - Heron, MT
  • Average UV index in September: 3

The month with the highest UV index is July (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 1).

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Average cloud cover in September
Heron, MT

Average cloud cover in September - Heron, MT
  • Average cloud cover in September: 25

The month with the most cloud cover is January (Cloud cover 67).
The month with the least cloud cover is August (Cloud cover 14).

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Average visibility in September
Heron, MT

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

Months with the highest visibility are May, June, July, August and September (6mi).
Months with the lowest visibility are January, February and December (3mi).

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