September weather forecastIdaho Falls, ID
September
Weather in September
September brings early signs of autumn to Idaho Falls, imbuing the city with an entirely new atmosphere. The climate starts to cool, and humidity levels rise, setting a dramatic background for the colorful fall foliage. Conversely, a rare fall thunderstorm should not be ruled out owing to a rise in rainfall. Combined with less daylight hours, the weather symbolizes the gradual transition from the warmth of summer to the chilly embrace of the fast-approaching winter. As the city marches deeper into fall, every sunset seems to precede colder and shorter days.Temperature
In Idaho Falls, the average high-temperature in September decreases from a moderately hot 84.4°F (29.1°C) in August to a still warm 73.6°F (23.1°C). In Idaho Falls, the September nights descend to a significantly cooler average of 49.5°F (9.7°C) compared to daytime highs.Humidity
The average relative humidity in September in Idaho Falls, Idaho, is 41%.Rainfall
The wettest months are May and September, with an average 0.83" (21mm) of rainfall.Snowfall
Months with snowfall are January through May, September through December. September is the first month it typically snows in Idaho Falls. Throughout September, in the average 0.1 snowfall days, it receives 0.04" (1mm) of snow. In Idaho Falls, during the entire year, snow falls for 54.4 days and aggregates up to 16.89" (429mm) of snow.Daylight
The average length of the day in September in Idaho Falls is 12h and 29min.On the first day of the month, sunrise is at 6:52 am and sunset at 8:02 pm. On the last day of September, sunrise is at 7:25 am and sunset at 7:10 pm MDT.
Sunshine
In September, the average sunshine is 10h.UV index
In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The maximum UV index, 4 during September, leads to the following recommendations:
Be vigilant - Preventing sunburn is recommended. Avoid the Sun's strongest UV rays by seeking shade and limiting exposure during midday. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage. Remember to consider! The UV radiation from the Sun can be intensified nearly twice by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Idaho Falls, ID
- Average high temperature in September: 73.6°F
The warmest month (with the highest average high temperature) is July (86.2°F).
The month with the lowest average high temperature is December (27.9°F).
- Average low temperature in September: 49.5°F
The month with the highest average low temperature is August (54.3°F).
The coldest month (with the lowest average low temperature) is January (14.2°F).
Average pressure in September
Idaho Falls, ID
- Average pressure in September: 29.98"Hg
The month with the highest atmospheric pressure is January (30.3"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Idaho Falls, ID
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is April (9mph).
The calmest month (with the lowest average wind speed) is January (5.8mph).
Average humidity in September
Idaho Falls, ID
- Average humidity in September: 41%
The month with the highest relative humidity is January (90%).
The month with the lowest relative humidity is August (35%).
Average rainfall in September
Idaho Falls, ID
- Average rainfall in September: 0.83"
The wettest months (with the highest rainfall) are May and September (0.83").
The driest month (with the least rainfall) is July (0.35").
Average rainfall days in September
Idaho Falls, ID
- Average rainfall days in September: 8.1 days
The month with the highest number of rainy days is May (10.7 days).
The month with the least rainy days is January (3.7 days).
Average snowfall in September
Idaho Falls, ID
- Average snowfall in September: 0.04"
The month with the highest snowfall is January (3.86").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Idaho Falls, ID
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is December (12.9 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Idaho Falls, ID
- Average daylight in September: 12h and 30min
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: 10h and 0min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is January (Average sunshine: 4h and 42min).
Average sunshine days in September
Idaho Falls, ID
- Average sunshine days in September: 19.4 days
The month with the most sunshine days is October (22.1 days).
The month with the least sunshine days is February (16.2 days).
Average UV index in September
Idaho Falls, ID
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).
Average cloud cover in September
Idaho Falls, ID
- Average cloud cover in September: 16
The months with the most cloud cover are January and February (Cloud cover 51).
The months with the least cloud cover are July and August (Cloud cover 11).
Average visibility in September
Idaho Falls, ID
- Average visibility in September: 6mi
The months with the highest visibility are March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and February (4mi).
