September weather forecast and climate
Hamilton, MT

A strong suspension bridge over a fast river in Hamilton, Montana, overlooking scenic trees and hilly landscapes over the other side of the shore
A strong suspension bridge over a fast river in Hamilton, Montana, overlooking scenic trees and hilly landscapes over the other side of the shore
The first month of the autumn, September, is still a comfortable month in Hamilton, Montana, with average temperature fluctuating between 39.9°F (4.4°C) and 66.2°F (19°C).

Temperature

In September, the average high-temperature decreases, from a moderately hot 76.3°F (24.6°C) in August, to an enjoyable 66.2°F (19°C). In Hamilton, Montana, in September, the average low-temperature is 39.9°F (4.4°C).

Humidity

In Hamilton, the average relative humidity in September is 57%.

Rainfall

In Hamilton, during September, the rain falls for 9.9 days and regularly aggregates up to 0.98" (25mm) of precipitation. Throughout the year, there are 163.6 rainfall days, and 20.83" (529mm) of precipitation is accumulated.

Snowfall

January through May, September through December are months with snowfall in Hamilton. September is the first month it typically snows. Throughout September, in the average 0.4 snowfall days, it receives 0.55" (14mm) of snow. In Hamilton, during the entire year, snow falls for 101.1 days, and aggregates up to 59.17" (1503mm) of snow.

Daylight

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

Sunshine

In September, the average sunshine is 9.5h.

UV index

In Hamilton, the average daily maximum UV index is 3. A UV Index value of 3 to 5 symbolizes a medium health hazard from unprotected exposure to the Sun's UV rays for the ordinary person.
Note: The daily maximum UV index of 3 interpret into the following advice:
Take precautions - Protection against sunburn is recommended. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. 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 Hamilton?

In September, the average high-temperature is 66.2°F (19°C), and the average low-temperature is 39.9°F (4.4°C).

What is the average humidity in September in Hamilton?

In September, the average relative humidity in Hamilton, Montana, is 57%.

How much does it rain in Hamilton in September?

In Hamilton, Montana, during September, the rain falls for 9.9 days and regularly aggregates up to 0.98" (25mm) of precipitation.

When does it start snowing in Hamilton?

September is the first month it typically snows in Hamilton, Montana. Throughout September, in the average 0.4 snowfall days, it receives 0.55" (14mm) of snow.

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

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

How many hours of sunshine does Hamilton have in September?

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

What is the UV index reading in September in Hamilton?

In September, the average daily maximum UV index in Hamilton is 3. A UV Index reading of 3 to 5 represents a moderate vulnerability from unsafe exposure to the Sun's UV rays.
Average temperature in September - Hamilton, MT
  • Average high temperature in September: 19°C

The warmest month (with the highest average high temperature) is July (25°C).
The month with the lowest average high temperature is December (-2.9°C).

  • Average low temperature in September: 4.4°C

The month with the highest average low temperature is August (8.3°C).
The coldest month (with the lowest average low temperature) is December (-10°C).

Average pressure in September - Hamilton, MT
  • Average pressure in September: 1015.6mbar

The month with the highest atmospheric pressure is January (1023mbar).
The month with the lowest atmospheric pressure is June (1013.7mbar).

Average wind speed in September - Hamilton, MT
  • Average wind speed in September: 7.1km/h

The windiest month (with the highest average wind speed) is January (8.6km/h).
The calmest month (with the lowest average wind speed) is August (6.6km/h).

Average humidity in September - Hamilton, MT
  • Average humidity in September: 57%

The month with the highest relative humidity is January (89%).
The month with the lowest relative humidity is August (50%).

Average rainfall in September - Hamilton, MT
  • Average rainfall in September: 25mm

The wettest months (with the highest rainfall) are February and April (60mm).
The driest month (with the least rainfall) is August (19mm).

Average rainfall days in September - Hamilton, MT
  • Average rainfall days in September: 9.9 days

The month with the highest number of rainy days is May (19.5 days).
The month with the least rainy days is July (8 days).

Average snowfall in September - Hamilton, MT
  • Average snowfall in September: 14mm

The month with the highest snowfall is February (331mm).
Months with the least snowfall are June, July and August (0mm).

Average snowfall days in September - Hamilton, MT
  • Average snowfall days in September: 0.4 days

The month with the highest number of snowfall days is February (19.3 days).
Months with the least snowfall days are June, July and August (0 days).

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

The month with the longest days is June (Average daylight: 15.7h).
The month with the shortest days is December (Average daylight: 8.7h).

  • Average sunshine in September: 9.5h

Months with the most sunshine are July and August (Average sunshine: 11.7h).
Months with the least sunshine are January and December (Average sunshine: 5.4).

Average sunshine days in September - Hamilton, MT
  • Average sunshine days in September: 16.1 days

The month with the most sunshine days is July (18.9 days).
The month with the least sunshine days is February (5.6 days).

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

The month with the highest UV index is July (UV index 5).
Months with the lowest UV index are February and December (UV index 1).

Average visibility in September - Hamilton, MT
  • Average visibility in September: 9km

Months with the highest visibility are July and August (10km).
Months with the lowest visibility are January, February, March and December (7km).