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
During the shift to September, a minor reduction in average high-temperature is observed, shifting from 80.2°F (26.8°C) in August to a still moderately hot 74.7°F (23.7°C). Grinnell sees an average low-temperature of 55.8°F (13.2°C) during September.Humidity
In September, the average relative humidity is 77%.Rainfall
In September, the rain falls for 10.6 days. Throughout September, 1.26" (32mm) of precipitation is accumulated. Throughout the year, in Grinnell, there are 117.5 rainfall days, and 13.03" (331mm) of precipitation is accumulated.Snowfall
June through September are months without snowfall.Daylight
In Grinnell, the average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:37 am and sunset at 7:43 pm. On the last day of September, sunrise is at 7:07 am and sunset at 6:53 pm CDT.
Sunshine
The average sunshine in September in Grinnell is 9.5h.UV index
In Grinnell, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a moderate threat to health from unsafe exposure to UV radiation for the average person.Note: In September, the UV index of 4 transforms into the following advice:
Take necessary precautions - Defending against sun damage is advocated. Minimize direct exposure to the Sun during midday when its radiation is at its peak. Outfit yourself in sun-safe attire, like long sleeves, pants, a hat, and UV-blocking sunglasses.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in Grinnell in September?
What is the average humidity in September in Grinnell?
How many days does it rain in September in Grinnell?
When it does not snow in Grinnell?
Does it snow in Grinnell in September?
What is the average length of the day in September in Grinnell?
When is the sunrise / sunset in September in Grinnell?
How many hours of sunshine does Grinnell have in September?
How high is the UV index in September in Grinnell?
Average temperature in September
Grinnell, IA
- Average high temperature in September: 74.7°F
The warmest month (with the highest average high temperature) is July (81.1°F).
The month with the lowest average high temperature is January (27°F).
- Average low temperature in September: 55.8°F
The month with the highest average low temperature is July (64.8°F).
The coldest month (with the lowest average low temperature) is January (13.8°F).
Average pressure in September
Grinnell, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Grinnell, IA
- Average wind speed in September: 8.1mph
The windiest month (with the highest average wind speed) is April (10.7mph).
The calmest month (with the lowest average wind speed) is August (7mph).
Average humidity in September
Grinnell, IA
- Average humidity in September: 77%
The month with the highest relative humidity is January (84%).
The month with the lowest relative humidity is October (71%).
Average rainfall in September
Grinnell, IA
- Average rainfall in September: 1.26"
The wettest months (with the highest rainfall) are May and June (1.97").
The driest month (with the least rainfall) is January (0.47").
Average rainfall days in September
Grinnell, IA
- Average rainfall days in September: 10.6 days
The month with the highest number of rainy days is June (15.1 days).
The month with the least rainy days is February (4.1 days).
Average snowfall in September
Grinnell, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (1.81").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Grinnell, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.1 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Grinnell, 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 3min
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 6min).
Average sunshine days in September
Grinnell, IA
- Average sunshine days in September: 17.9 days
The month with the most sunshine days is January (21.1 days).
The month with the least sunshine days is June (11.5 days).
Average UV index in September
Grinnell, IA
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Grinnell, IA
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 55).
The month with the least cloud cover is September (Cloud cover 29).
Average visibility in September
Grinnell, IA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are July and August (5mi).
Grinnell, Iowa, USA
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