September weather forecast
Boise, ID

The golden fall season in Boise, Idaho
The golden fall season in Boise, Idaho

Weather in September

The first month of the autumn, September, is still a warm month in Boise, Idaho, with temperature in the range of an average high of 76.1°F (24.5°C) and an average low of 53.6°F (12°C).

Temperature

In September, the average high-temperature decreases from a hot 86.5°F (30.3°C) in August to a warm 76.1°F (24.5°C). In September, in Boise, the average low-temperature is 53.6°F (12°C).

Humidity

The average relative humidity in September is 37%.

Rainfall

In September, the rain falls for 6.7 days. Throughout September, 0.39" (10mm) of precipitation is accumulated. Throughout the year, there are 116.8 rainfall days, and 15.08" (383mm) of precipitation is accumulated.

Snowfall

In Boise, snow does not fall in May through October.

Daylight

In September, the average length of the day is 12h and 29min.
On the first day of September in Boise, sunrise is at 7:08 am and sunset at 8:20 pm. On the last day of the month, sunrise is at 7:41 am and sunset at 7:28 pm MDT.

Sunshine

The average sunshine in September is 9.5h.

UV index

In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for ordinary individuals.
Note: The average daily UV index of 4 in September transform into the following instructions:
Take precautions - Protection against sun damage is advised. 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.
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FAQ

What is the temperature in September in Boise?

In Boise, Idaho, in September, the average high-temperature is 76.1°F (24.5°C), and the average low-temperature is 53.6°F (12°C).

What is the average humidity in September in Boise?

The average relative humidity in September in Boise is 37%.

How much does it rain in Boise in September?

In Boise, Idaho, in September, it is raining for 6.7 days, with typically 0.39" (10mm) of accumulated precipitation.

When it does not snow in Boise?

May through October are months without snowfall in Boise.

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

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

When is the sunrise / sunset in September in Boise?

In September, on the first day of the month, sunrise is at 7:08 am and sunset at 8:20 pm. On the last day of the month, sunrise is at 7:41 am and sunset at 7:28 pm MDT.

How long on average sun shines in September in Boise?

The average sunshine duration in September in Boise, Idaho, is 9.5h.

What is the UV index reading in September in Boise?

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

Average temperature in September
Boise, ID

Average temperature in September - Boise, ID
  • Average high temperature in September: 76.1°F

The warmest month (with the highest average high temperature) is July (87.8°F).
The month with the lowest average high temperature is December (34.7°F).

  • Average low temperature in September: 53.6°F

The month with the highest average low temperature is August (61.3°F).
The coldest month (with the lowest average low temperature) is December (23.2°F).

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Average pressure in September
Boise, ID

Average pressure in September - Boise, ID
  • Average pressure in September: 29.94"Hg

The month with the highest atmospheric pressure is January (30.25"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).

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Average wind speed in September
Boise, ID

Average wind speed in September - Boise, ID
  • Average wind speed in September: 5.4mph

The windiest month (with the highest average wind speed) is April (7.1mph).
The calmest month (with the lowest average wind speed) is January (5.2mph).

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Average humidity in September
Boise, ID

Average humidity in September - Boise, ID
  • Average humidity in September: 37%

The month with the highest relative humidity is January (80%).
The month with the lowest relative humidity is July (30%).

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Average rainfall in September
Boise, ID

Average rainfall in September - Boise, ID
  • Average rainfall in September: 0.39"

The wettest month (with the highest rainfall) is March (2.2").
The driest month (with the least rainfall) is July (0.2").

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Average rainfall days in September
Boise, ID

Average rainfall days in September - Boise, ID
  • Average rainfall days in September: 6.7 days

The month with the highest number of rainy days is March (16.2 days).
The month with the least rainy days is July (4.5 days).

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Average snowfall in September
Boise, ID

Average snowfall in September - Boise, ID
  • Average snowfall in September: 0"

The month with the highest snowfall is December (6.65").
The months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in September
Boise, ID

Average snowfall days in September - Boise, ID
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is December (9.2 days).
The months with the least snowfall days are June, July, August and September (0 days).

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Average daylight in September /
Average sunshine in September
Boise, ID

Average daylight in September / Average sunshine in September - Boise, ID
  • Average daylight in September: 12h and 29min

The month with the longest days is June (Average daylight: 15h and 23min).
The month with the shortest days is December (Average daylight: 9h and 0min).

  • Average sunshine in September: 9h and 30min

The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 5h and 30min).

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Average sunshine days in September
Boise, ID

Average sunshine days in September - Boise, ID
  • Average sunshine days in September: 21.5 days

The month with the most sunshine days is July (23.6 days).
The month with the least sunshine days is March (12.1 days).

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Average UV index in September
Boise, ID

Average UV index in September - Boise, ID
  • 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
Boise, ID

Average cloud cover in September - Boise, ID
  • Average cloud cover in September: 14

The month with the most cloud cover is December (Cloud cover 42).
The month with the least cloud cover is July (Cloud cover 8).

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Average visibility in September
Boise, ID

Average visibility in September - Boise, ID
  • Average visibility in September: 6mi

The months with the highest visibility are February, March, April, May, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is January (5mi).

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