September weather forecast
Nampa, ID

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Weather in September

September brings the departure of summer and welcomes the onset of autumn in Nampa. A subtle drop in temperature brings relief from the scorching heat of previous months. With declining UV index and temperatures, the evening becomes pleasant accentuating the beauty of the city. September serves as a bridge or transition between the warm summer and cooler autumn. While the daytime temperature remains warm, arrival of cooler evenings announce the advent of fall.

Temperature

The average high-temperature in Nampa drops in September, from August's tropical 89.8°F (32.1°C) to a warm 79°F (26.1°C). Nampa observes a noteworthy temperature drop from the daily highs during September nights, with a mean temperature of 55.9°F (13.3°C).

Humidity

The average relative humidity in September is 35%.

Rainfall

In Nampa, in September, during 4.9 rainfall days, 0.2" (5mm) of precipitation is typically accumulated. In Nampa, Idaho, during the entire year, the rain falls for 98.5 days and collects up to 9.69" (246mm) of precipitation.

Snowfall

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

Daylight

The average length of the day in September is 12h and 29min.
On the first day of the month, sunrise is at 7:11 am and sunset at 8:20 pm. On the last day of September, in Nampa, sunrise is at 7:43 am and sunset at 7:28 pm MDT.

Sunshine

In September, the average sunshine is 9.5h.

UV index

In Nampa, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for average individuals.
Note: In September, the UV index of 5 transforms into the following advice:
Act with care - The need to guard against sun damage is communicated. Avoiding direct sunlight during midday hours helps reduce the risk from intense UV radiation. Wearing sunglasses with both UVA and UVB protection effectively reduces sun-induced eye damage.
Updated: Feb 12, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are the temperatures in Nampa in September?

In September, in Nampa, the average high-temperature is 79°F (26.1°C), and the average low-temperature is 55.9°F (13.3°C).

What is the average humidity in September in Nampa?

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

How many days does it rain in September in Nampa?

In Nampa, Idaho, during September, the rain falls for 4.9 days and regularly aggregates up to 0.2" (5mm) of precipitation.

When it does not snow in Nampa?

In Nampa, Idaho, snow does not fall in May through October.

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

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

What time are sunrise and sunset in September in Nampa?

In September, on the first day of the month, sunrise is at 7:11 am and sunset at 8:20 pm. On the last day of the month, sunrise is at 7:43 am and sunset at 7:28 pm MDT.

How long on average sun shines in September in Nampa?

In Nampa, the average sunshine duration in September is 9.5h.

What is the UV index reading in September in Nampa?

In September, the average daily maximum UV index in Nampa, Idaho, is 5. A UV Index of 3 to 5 symbolizes a medium hazard to health from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Nampa, ID

Average temperature in September - Nampa, ID
  • Average high temperature in September: 79°F

The warmest month (with the highest average high temperature) is July (91°F).
The month with the lowest average high temperature is December (36.5°F).

  • Average low temperature in September: 55.9°F

The month with the highest average low temperature is August (63.3°F).
The coldest month (with the lowest average low temperature) is December (25.7°F).

Average pressure in September
Nampa, ID

Average pressure in September - Nampa, 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).

Average wind speed in September
Nampa, ID

Average wind speed in September - Nampa, ID
  • Average wind speed in September: 6mph

The windiest month (with the highest average wind speed) is April (7.9mph).
The calmest month (with the lowest average wind speed) is January (5.8mph).

Average humidity in September
Nampa, ID

Average humidity in September - Nampa, ID
  • Average humidity in September: 35%

The month with the highest relative humidity is January (78%).
The months with the lowest relative humidity are July and August (29%).

Average rainfall in September
Nampa, ID

Average rainfall in September - Nampa, ID
  • Average rainfall in September: 0.2"

The wettest month (with the highest rainfall) is March (1.46").
The driest months (with the least rainfall) are July and August (0.12").

Average rainfall days in September
Nampa, ID

Average rainfall days in September - Nampa, ID
  • Average rainfall days in September: 4.9 days

The month with the highest number of rainy days is March (14.3 days).
The month with the least rainy days is August (3.1 days).

Average snowfall in September
Nampa, ID

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

The month with the highest snowfall is January (3.23").
The months with the least snowfall are May, June, July, August, September and October (0").

Average snowfall days in September
Nampa, ID

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

The month with the highest number of snowfall days is December (6.6 days).
The months with the least snowfall days are May, June, July, August and September (0 days).

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

Average daylight in September / Average sunshine in September - Nampa, ID
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).

  • Average sunshine in September: 9h and 3min

The month with the most sunshine is July (Average sunshine: 12h and 0min).
The months with the least sunshine are January and December (Average sunshine: 5h and 48min).

Average sunshine days in September
Nampa, ID

Average sunshine days in September - Nampa, ID
  • Average sunshine days in September: 23.3 days

The month with the most sunshine days is July (25.7 days).
The month with the least sunshine days is March (14 days).

Average UV index in September
Nampa, ID

Average UV index in September - Nampa, ID
  • Average UV index in September: 5

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).

Average cloud cover in September
Nampa, ID

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

The months with the most cloud cover are January and December (Cloud cover 39).
The month with the least cloud cover is July (Cloud cover 8).

Average visibility in September
Nampa, ID

Average visibility in September - Nampa, ID
  • 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).

Nampa, Idaho, USA

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