September weather forecastLewiston, ID
September
Weather in September
Lewiston's September climate marks the beginning of mild autumnal conditions from the hot summer of August. Cooler temperatures begin to creep in, especially during the mornings, making the climate more bearable. The UV index starts to decline and the hours of sunshine decrease, aligning with the shortening of days. With rainfall frequency remaining low, the clear skies allow breathtaking views of autumnal hues. As the wind speed remains steady, clear evenings provide an ideal setting for stargazing.Temperature
As August transitions to September, the average high-temperature falls from a moderately hot 85.3°F (29.6°C) to a still warm 75°F (23.9°C). September nights see a notable contrast from daytime highs, with the nighttime temperature averaging at a cool 52.7°F (11.5°C).Humidity
The average relative humidity in September is 45%.Rainfall
In Lewiston, in September, it is raining for 6.7 days, with typically 0.39" (10mm) of accumulated precipitation. Throughout the year, there are 142.4 rainfall days, and 14.21" (361mm) of precipitation is accumulated.Snowfall
In Lewiston, snow does not fall in May through September.Daylight
In Lewiston, the average length of the day in September is 12h and 32min.On the first day of the month, sunrise is at 6:09 am and sunset at 7:26 pm. On the last day of September, in Lewiston, sunrise is at 6:46 am and sunset at 6:29 pm PDT.
Sunshine
In Lewiston, the average sunshine in September is 10.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for the average person.Note: In September, the maximum UV index of 4 suggests these recommendations:
Take precautions - Protection against sun damage is advised. Considering the strength of solar radiation at midday, one should avoid direct Sun exposure. Clothes that are both tight-knit and comfortably loose are prime choices for sun protection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Lewiston, ID
- Average high temperature in September: 75°F
The warmest month (with the highest average high temperature) is August (85.3°F).
The month with the lowest average high temperature is December (36.1°F).
- Average low temperature in September: 52.7°F
The month with the highest average low temperature is August (59.2°F).
The coldest month (with the lowest average low temperature) is December (24.4°F).
Average pressure in September
Lewiston, ID
- Average pressure in September: 29.96"Hg
The month with the highest atmospheric pressure is January (30.2"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).
Average wind speed in September
Lewiston, ID
- Average wind speed in September: 4.3mph
The windiest month (with the highest average wind speed) is April (5.7mph).
The calmest months (with the lowest average wind speed) are July, August and September (4.3mph).
Average humidity in September
Lewiston, ID
- Average humidity in September: 45%
The month with the highest relative humidity is January (84%).
The month with the lowest relative humidity is August (38%).
Average rainfall in September
Lewiston, ID
- Average rainfall in September: 0.39"
The wettest month (with the highest rainfall) is March (1.85").
The driest month (with the least rainfall) is August (0.31").
Average rainfall days in September
Lewiston, ID
- Average rainfall days in September: 6.7 days
The month with the highest number of rainy days is March (17.6 days).
The month with the least rainy days is August (5.2 days).
Average snowfall in September
Lewiston, ID
- Average snowfall in September: 0"
The month with the highest snowfall is February (3.27").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Lewiston, ID
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (8.1 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
Lewiston, ID
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).
- Average sunshine in September: 10h and 24min
The month with the most sunshine is August (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 5h and 6min).
Average sunshine days in September
Lewiston, ID
- Average sunshine days in September: 21.9 days
The month with the most sunshine days is July (24 days).
The months with the least sunshine days are February and March (10.8 days).
Average UV index in September
Lewiston, ID
- Average UV index in September: 4
The month with the highest UV index is July (UV index 7).
The month with the lowest UV index is February (UV index 1).
Average cloud cover in September
Lewiston, ID
- Average cloud cover in September: 18
The month with the most cloud cover is February (Cloud cover 48).
The months with the least cloud cover are July and August (Cloud cover 12).
Average visibility in September
Lewiston, 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, February and December (5mi).
