September weather forecast
Riverton, WY

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Weather in September

With temperatures falling to a slightly chillier 75.6°F (24.2°C), September sees the commencement of autumn in Riverton. As summer transitions into fall, a mere 0.55" (14mm) of rainfall make it the driest period of the year. The change in season brings about a spectacular sight of falling leaves, whipped about the town by the persistent breeze. September days gradually grow shorter, hinting at an imminent shift of the season. The general mood in Riverton in September is a splendid blend of pleasant warmth and crisp cool, a transitional time that bridges summer and fall beautifully.

Temperature

A shift in Riverton's weather is observed as August turns into September, with the average high temperature reducing from a warm 84.9°F (29.4°C) to a still moderately hot 75.6°F (24.2°C). Despite the significant gap from daytime peaks, Riverton experiences an average low-temperature of 52.9°F (11.6°C) in September.

Humidity

In September, the average relative humidity in Riverton is 35%.

Rainfall

In Riverton, in September, it is raining for 6 days, with typically 0.55" (14mm) of accumulated precipitation. In Riverton, during the entire year, the rain falls for 67.3 days and collects up to 6.93" (176mm) of precipitation.

Snowfall

Months with snowfall are January through May, September through December. September is the first month it typically snows in Riverton, Wyoming. Throughout September, in the average 0.3 snowfall days, it receives 0.63" (16mm) of snow. Throughout the year, in Riverton, there are 42.8 snowfall days, and 25.47" (647mm) of snow is accumulated.

Daylight

The average length of the day in September in Riverton is 12h and 29min.
On the first day of the month, sunrise is at 6:38 am and sunset at 7:47 pm. On the last day of September, sunrise is at 7:10 am and sunset at 6:55 pm MDT.

Sunshine

In Riverton, the average sunshine in September is 10.7h.

UV index

In September, the average daily maximum UV index is 4. A UV Index of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV radiation for ordinary individuals.
Note: The maximum UV index of 4 during September translates into these guidelines:
Take precautions. Light skin individuals may get burned in less than 30 minutes. During midday, the Sun's radiation is strongest, and it's advisable to reduce direct exposure. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes. Be informed! The Sun's UV radiation can be nearly doubled due to the reflection from snow.
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Frequently asked questions

What is the temperature in September in Riverton?

In Riverton, in September, the average high-temperature is 75.6°F (24.2°C), and the average low-temperature is 52.9°F (11.6°C).

What is the average humidity in September in Riverton?

The average relative humidity in September is 35%.

How much does it rain in Riverton in September?

In Riverton, during September, the rain falls for 6 days and regularly aggregates up to 0.55" (14mm) of precipitation.

When does it start to snow in Riverton?

September is the first month it typically snows in Riverton, Wyoming. Throughout September, in the average 0.3 snowfall days, it receives 0.63" (16mm) of snow.

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

In Riverton, Wyoming, the average day length in September is 12h and 29min.

When is the sunrise / sunset in September in Riverton?

On the first day of September in Riverton, sunrise is at 6:38 am and sunset at 7:47 pm. On the last day of the month, sunrise is at 7:10 am and sunset at 6:55 pm MDT.

How many hours of sunshine does Riverton have in September?

In Riverton, the average sunshine duration in September is 10.7h.

How high is the UV index in September in Riverton?

In September, the average daily maximum UV index in Riverton, Wyoming, is 4. A UV Index estimate of 3 to 5 represents a medium hazard to health from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Riverton, WY

Average temperature in September - Riverton, WY
  • Average high temperature in September: 75.6°F

The warmest month (with the highest average high temperature) is July (87.1°F).
The month with the lowest average high temperature is December (30.9°F).

  • Average low temperature in September: 52.9°F

The month with the highest average low temperature is July (61.5°F).
The coldest month (with the lowest average low temperature) is January (14.5°F).

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Average pressure in September
Riverton, WY

Average pressure in September - Riverton, WY
  • Average pressure in September: 29.98"Hg

The month with the highest atmospheric pressure is January (30.22"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).

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Average wind speed in September
Riverton, WY

Average wind speed in September - Riverton, WY
  • Average wind speed in September: 6.5mph

The windiest month (with the highest average wind speed) is June (7.5mph).
The calmest month (with the lowest average wind speed) is January (5.5mph).

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Average humidity in September
Riverton, WY

Average humidity in September - Riverton, WY
  • Average humidity in September: 35%

The month with the highest relative humidity is January (77%).
The months with the lowest relative humidity are July and August (31%).

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Average rainfall in September
Riverton, WY

Average rainfall in September - Riverton, WY
  • Average rainfall in September: 0.55"

The wettest month (with the highest rainfall) is May (1.42").
The driest month (with the least rainfall) is January (0.24").

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Average rainfall days in September
Riverton, WY

Average rainfall days in September - Riverton, WY
  • Average rainfall days in September: 6 days

The month with the highest number of rainy days is May (9.9 days).
The month with the least rainy days is January (2.5 days).

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Average snowfall in September
Riverton, WY

Average snowfall in September - Riverton, WY
  • Average snowfall in September: 0.63"

The month with the highest snowfall is April (5.39").
The months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Riverton, WY

Average snowfall days in September - Riverton, WY
  • Average snowfall days in September: 0.3 days

The month with the highest number of snowfall days is February (7.8 days).
The months with the least snowfall days are July and August (0 days).

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Average daylight in September /
Average sunshine in September
Riverton, WY

Average daylight in September / Average sunshine in September - Riverton, WY
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).

  • Average sunshine in September: 10h and 4min

The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 6h and 36min).

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Average sunshine days in September
Riverton, WY

Average sunshine days in September - Riverton, WY
  • Average sunshine days in September: 20.2 days

The month with the most sunshine days is January (24.5 days).
The month with the least sunshine days is April (15.5 days).

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Average UV index in September
Riverton, WY

Average UV index in September - Riverton, WY
  • Average UV index in September: 4

The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in September
Riverton, WY

Average cloud cover in September - Riverton, WY
  • Average cloud cover in September: 13

The months with the most cloud cover are February and April (Cloud cover 28).
The months with the least cloud cover are July and August (Cloud cover 12).

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Average visibility in September
Riverton, WY

Average visibility in September - Riverton, WY
  • Average visibility in September: 6mi

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

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Riverton, Wyoming, USA

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