Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
With the onset of September, a modest change to a still moderately hot 74.3°F (23.5°C) from August's 79.5°F (26.4°C) is noted in high-temperature. An average low-temperature of 55°F (12.8°C) is expected during September.Humidity
In Keystone, the average relative humidity in September is 78%.Rainfall
In Keystone, in September, it is raining for 11.9 days, with typically 2.52" (64mm) of accumulated precipitation. In Keystone, during the entire year, the rain falls for 139 days and collects up to 29.49" (749mm) of precipitation.Snowfall
June through September are months without snowfall in Keystone.Daylight
The average length of the day in September is 12h and 28min.On the first day of September, sunrise is at 6:35 am and sunset at 7:41 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:51 pm CDT.
Sunshine
The average sunshine in September is 9.2h.UV index
In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a moderate health risk from unsafe exposure to UV radiation for the average person.Note: A typical high UV index of 4 in September suggests the following recommendations:
Undertake precautions - Obligation exists to protect against skin and eye damage. UV radiation is strongest from the Sun during midday; protect yourself by staying in shaded areas. A hat with a broad brim is indispensable, filtering out up to half of UV rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the average September temperature?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
Does it snow in September?
How many hours of daylight does Keystone have in September?
When are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index reading in September in Keystone?
Average temperature in September
Keystone, IA
- Average high temperature in September: 74.3°F
The warmest month (with the highest average high temperature) is July (80.8°F).
The month with the lowest average high temperature is January (25.9°F).
- Average low temperature in September: 55°F
The month with the highest average low temperature is July (64.4°F).
The coldest month (with the lowest average low temperature) is January (13.5°F).
Average pressure in September
Keystone, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Keystone, IA
- Average wind speed in September: 8.1mph
The windiest month (with the highest average wind speed) is April (10.8mph).
The calmest month (with the lowest average wind speed) is August (7mph).
Average humidity in September
Keystone, IA
- Average humidity in September: 78%
The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is October (72%).
Average rainfall in September
Keystone, IA
- Average rainfall in September: 2.52"
The wettest month (with the highest rainfall) is May (4.61").
The driest month (with the least rainfall) is January (1.18").
Average rainfall days in September
Keystone, IA
- Average rainfall days in September: 11.9 days
The month with the highest number of rainy days is June (19.3 days).
The month with the least rainy days is January (4.5 days).
Average snowfall in September
Keystone, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (5.24").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Keystone, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (10.6 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Keystone, IA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in September: 9h and 1min
The month with the most sunshine is July (Average sunshine: 9h and 54min).
The month with the least sunshine is January (Average sunshine: 4h and 0min).
Average sunshine days in September
Keystone, IA
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is October (19.2 days).
The month with the least sunshine days is June (8.4 days).
Average UV index in September
Keystone, IA
- Average UV index in September: 4
The month with the highest UV index is June (UV index 6).
The months with the lowest UV index are January, February, October, November and December (UV index 2).
Average cloud cover in September
Keystone, IA
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 57).
The month with the least cloud cover is September (Cloud cover 30).
Average visibility in September
Keystone, IA
- Average visibility in September: 6mi
The months with the highest visibility are February, March, April, May, June, August, September, October, November and December (6mi).
The months with the lowest visibility are January and July (5mi).
Keystone, Iowa, USA
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