September weather forecastDerby, IA
September
Weather in September
The first month of the autumn, September, is also a moderately hot month in Derby, Iowa, with an average temperature ranging between min 56.3°F (13.5°C) and max 75.7°F (24.3°C).Temperature
The onset of September aligns with a soft reduction in the average high-temperature, gently falling from a warm 81.7°F (27.6°C) in August to a still moderately hot 75.7°F (24.3°C). Derby's average low-temperature in September is measured at a moderate 56.3°F (13.5°C).Humidity
In September, the average relative humidity is 77%.Rainfall
In Derby, in September, it is raining for 11.5 days, with typically 2.72" (69mm) of accumulated precipitation. Throughout the year, in Derby, there are 131.1 rainfall days, and 25.71" (653mm) of precipitation is accumulated.Snowfall
In Derby, Iowa, snow does not fall in June through September.Daylight
In Derby, Iowa, the average length of the day in September is 12h and 27min.On the first day of September in Derby, sunrise is at 6:41 am and sunset at 7:45 pm. On the last day of the month, sunrise is at 7:10 am and sunset at 6:56 pm CDT.
Sunshine
In Derby, the average sunshine in September is 9.2h.UV index
The average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for average individuals.Note: The UV index of 4 during September translates into the following guidance:
Exercise care. People with light skin might get burns in fewer than 30 minutes. The mid-day Sun emits the most powerful UV radiation, so seek shade and minimize exposure. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Derby, IA
- Average high temperature in September: 75.7°F
The warmest month (with the highest average high temperature) is July (83.1°F).
The month with the lowest average high temperature is January (29.3°F).
- Average low temperature in September: 56.3°F
The month with the highest average low temperature is July (65.7°F).
The coldest month (with the lowest average low temperature) is January (16°F).
Average pressure in September
Derby, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Derby, IA
- Average wind speed in September: 8.1mph
The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (7.1mph).
Average humidity in September
Derby, IA
- Average humidity in September: 77%
The month with the highest relative humidity is June (83%).
The month with the lowest relative humidity is October (72%).
Average rainfall in September
Derby, IA
- Average rainfall in September: 2.72"
The wettest month (with the highest rainfall) is June (3.74").
The driest month (with the least rainfall) is January (0.94").
Average rainfall days in September
Derby, IA
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is May (16.7 days).
The month with the least rainy days is January (4.7 days).
Average snowfall in September
Derby, IA
- Average snowfall in September: 0"
The month with the highest snowfall is February (4.13").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Derby, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (10.2 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Derby, IA
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 9h and 12min
The month with the most sunshine is July (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 4h and 12min).
Average sunshine days in September
Derby, IA
- Average sunshine days in September: 16.9 days
The month with the most sunshine days is November (19.3 days).
The month with the least sunshine days is June (10.7 days).
Average UV index in September
Derby, IA
- Average UV index in September: 4
The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Derby, IA
- Average cloud cover in September: 31
The month with the most cloud cover is January (Cloud cover 54).
The months with the least cloud cover are July and August (Cloud cover 30).
Average visibility in September
Derby, IA
- Average visibility in September: 6mi
The months with the highest visibility are February, March, April, May, June, July, September, October, November and December (6mi).
The months with the lowest visibility are January and August (5mi).
