Flagstaff
Arizona, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Flagstaff, AZ

A close-up of the brown iconic clock tower in the city of Flagstaff, Arizona, with the street signs of Birch Avenue and San Francisco Street
A close-up of the brown iconic clock tower in the city of Flagstaff, Arizona, with the street signs of Birch Avenue and San Francisco Street
September, the first month of the autumn, in Flagstaff, is also an agreeable month, with temperature in the range of an average low of 42.1°F (5.6°C) and an average high of 72.9°F (22.7°C).

Temperature

In Flagstaff, the average high-temperature marginally drops, from a moderately hot 78.4°F (25.8°C) in August, to a pleasant 72.9°F (22.7°C). In September, the average low-temperature is 42.1°F (5.6°C).

Humidity

The average relative humidity in September is 54.7%.

Rainfall

In Flagstaff, during 7.9 rainfall days, 2.4" (60.5mm) of precipitation is typically accumulated. Throughout the year, in Flagstaff, there are 87.7 rainfall days, and 21.9" (555.3mm) of precipitation is accumulated.

Snowfall

In Flagstaff, Arizona, in September, it doesn't snow. In October, it regularly snows. Throughout the year, in Flagstaff, Arizona, 101.7" (2583.3mm) of snow is accumulated.

Daylight

In September, the average length of the day is 12.4h.

Sunshine

In September, the average sunshine is 10h.

UV index

In September, the average daily maximum UV index in Flagstaff is 9. A UV Index of 8 to 10 symbolizes a very high threat to health from the exposure to the Sun's UV radiation for average individuals.
In September, the average maximum UV index of 9 translate into the following recommendations:
Take extra precautions. Protection against sun damage is required. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. 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.

What is the temperature in September in Flagstaff?

The average high-temperature, in September, in Flagstaff, Arizona, is 72.9°F (22.7°C), while the average low-temperature is 42.1°F (5.6°C).

What is the average humidity in September in Flagstaff?

In September, the average relative humidity in Flagstaff is 54.7%.

How many days does it rain in September in Flagstaff?

In Flagstaff, Arizona, in September, during 7.9 rainfall days, 2.4" (60.5mm) of precipitation is typically accumulated.

Does it snow in Flagstaff in September?

In Flagstaff, Arizona, in September, it doesn't snow. In October, it regularly snows.

How many hours of daylight does Flagstaff have in September?

The average length of the day in September in Flagstaff is 12.4h.

How long on average sun shines in September in Flagstaff?

The average sunshine in September is 10h.

How high is the UV index in September in Flagstaff?

In September, the average daily maximum UV index is 9. A UV Index estimate of 8 to 10 represents a very high health vulnerability from the exposure to the Sun's UV rays.
Average temperature in September - Flagstaff, AZ
  • Average high temperature in September: 72.9°F

The warmest month (with the highest average high temperature) is July (81.2°F).
Months with the lowest average high temperature are January and December (42.5°F).

  • Average low temperature in September: 42°F

The month with the highest average low temperature is July (50.9°F).
The coldest month (with the lowest average low temperature) is December (16.8°F).

Average humidity in September - Flagstaff, AZ
  • Average humidity in September: 54.7%

The month with the highest relative humidity is January (61.9%).
The month with the lowest relative humidity is June (33.6%).

Average rainfall in September - Flagstaff, AZ
  • Average rainfall in September: 2.4"

The wettest month (with the highest rainfall) is August (3.1").
The driest month (with the lowest rainfall) is June (0.4").

Average rainfall days in September - Flagstaff, AZ
  • Average rainfall days in September: 7.9 days

The month with the highest number of rainy days is August (14 days).
The month with the lowest number of rainy days is June (2.6 days).

Average snowfall in September - Flagstaff, AZ
  • Average snowfall in September: 0"

The month with the highest snowfall is January (23.2").
Months with the lowest snowfall are June, July, August and September (0").

Average snowfall days in September - Flagstaff, AZ
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (7.5 days).
Months with the lowest number of snowfall days are June, July, August and September (0 days).

Average daylight in September / Average sunshine in September - Flagstaff, AZ
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.5h).
The month with shortest days is December (Average daylight: 9.8h).

  • Average sunshine in September: 10h

The month with most sunshine is June (Average sunshine: 12.4h).
The month with least sunshine is December (Average sunshine: 7.1h).

Average UV index in September - Flagstaff, AZ
  • Average UV index in September: 9

The month with the highest UV index is July (UV index 12).
Months with the lowest UV index are January and December (UV index 3).