September weather forecast and climate
Roy, MT

September, the first month of the autumn, in Roy, is still a comfortable month, with average temperature ranging between max 67.5°F (19.7°C) and min 47.1°F (8.4°C).

Temperature

In Roy, Montana, the average high-temperature drops, from a warm 78.1°F (25.6°C) in August, to a comfortable 67.5°F (19.7°C). In Roy, Montana, the average low-temperature is 47.1°F (8.4°C).

Humidity

In September, the average relative humidity is 52%.

Rainfall

In September, the rain falls for 8.7 days. Throughout September, 1.02" (26mm) of precipitation is accumulated. In Roy, during the entire year, the rain falls for 126.2 days and collects up to 17.83" (453mm) of precipitation.

Snowfall

January through June, September through December are months with snowfall. September is the first month it typically snows. Throughout September, in the average 1 snowfall days, it receives 1.3" (33mm) of snow. In Roy, during the entire year, snow falls for 83.4 days, and aggregates up to 45.51" (1156mm) of snow.

Daylight

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

Sunshine

The average sunshine in September is 10h.

UV index

The average daily maximum UV index in Roy is 4. A UV Index value of 3 to 5 symbolizes a medium health hazard 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. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.

What is the temperature in September in Roy?

In September, in Roy, the average high-temperature is 67.5°F (19.7°C), and the average low-temperature is 47.1°F (8.4°C).

What is the average humidity in September in Roy?

In September, the average relative humidity in Roy is 52%.

How many days does it rain in September in Roy?

In Roy, Montana, during September, the rain falls for 8.7 days and regularly aggregates up to 1.02" (26mm) of precipitation.

When does it start snowing in Roy?

September is the first month it typically snows in Roy. Throughout September, in the average 1 snowfall days, it receives 1.3" (33mm) of snow.

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

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

How many hours of sunshine does Roy have in September?

In September, the average sunshine in Roy, Montana, is 10h.

How high is the UV index in September in Roy?

The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate health threat from the exposure to the Sun's UV rays.
Average temperature in September - Roy, MT
  • Average high temperature in September: 19.7°C

The warmest month (with the highest average high temperature) is July (26°C).
Months with the lowest average high temperature are February and December (-1.6°C).

  • Average low temperature in September: 8.4°C

The month with the highest average low temperature is August (12.5°C).
The coldest month (with the lowest average low temperature) is February (-9.3°C).

Average pressure in September - Roy, MT
  • Average pressure in September: 1013.8mbar

The month with the highest atmospheric pressure is January (1020.3mbar).
The month with the lowest atmospheric pressure is June (1010.9mbar).

Average wind speed in September - Roy, MT
  • Average wind speed in September: 13.6km/h

The windiest months (with the highest average wind speed) are January, April and October (15.9km/h).
The calmest month (with the lowest average wind speed) is August (11.9km/h).

Average humidity in September - Roy, MT
  • Average humidity in September: 52%

The month with the highest relative humidity is February (79%).
The month with the lowest relative humidity is August (47%).

Average rainfall in September - Roy, MT
  • Average rainfall in September: 26mm

The wettest month (with the highest rainfall) is May (86mm).
The driest month (with the least rainfall) is December (18mm).

Average rainfall days in September - Roy, MT
  • Average rainfall days in September: 8.7 days

The month with the highest number of rainy days is May (19.3 days).
The month with the least rainy days is January (5.4 days).

Average snowfall in September - Roy, MT
  • Average snowfall in September: 33mm

The month with the highest snowfall is April (232mm).
Months with the least snowfall are July and August (0mm).

Average snowfall days in September - Roy, MT
  • Average snowfall days in September: 1 days

The month with the highest number of snowfall days is February (15.2 days).
Months with the least snowfall days are July and August (0 days).

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

The month with the longest days is June (Average daylight: 15.9h).
The month with the shortest days is December (Average daylight: 8.5h).

  • Average sunshine in September: 10h

The month with the most sunshine is July (Average sunshine: 11.8h).
The month with the least sunshine is February (Average sunshine: 5.5h).

Average sunshine days in September - Roy, MT
  • Average sunshine days in September: 19.3 days

The month with the most sunshine days is September (19.3 days).
The month with the least sunshine days is April (8.3 days).

Average UV index in September - Roy, 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, April, October, November and December (UV index 2).

Average cloud cover in September - Roy, MT
  • Average cloud cover in September: 23

The month with the most cloud cover is February (Cloud cover 45).
The month with the least cloud cover is July (Cloud cover 16).

Average visibility in September - Roy, MT
  • Average visibility in September: 10km

Months with the highest visibility are June, July, August and September (10km).
Months with the lowest visibility are January, February, March, April, May, October, November and December (9km).