September weather forecast
Grand River, IA

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Weather in September

The first month of the autumn, September, is still a warm month in Grand River, Iowa, with an average temperature ranging between max 76.1°F (24.5°C) and min 56.3°F (13.5°C).

Temperature

September signifies a gentle decline in Grand River's average high-temperature, easing from a moderately hot 81.9°F (27.7°C) in August to a still warm 76.1°F (24.5°C). Throughout September, Grand River experiences a low-temperature average of 56.3°F (13.5°C).

Humidity

In Grand River, the average relative humidity in September is 77%.

Rainfall

In Grand River, in September, it is raining for 11.5 days, with typically 2.24" (57mm) of accumulated precipitation. In Grand River, during the entire year, the rain falls for 132.4 days and collects up to 20.24" (514mm) of precipitation.

Snowfall

In Grand River, Iowa, snow does not fall in June through September.

Daylight

The average length of the day in September is 12h and 27min.
On the first day of the month, sunrise is at 6:43 am and sunset at 7:47 pm. On the last day of September, sunrise is at 7:12 am and sunset at 6:58 pm CDT.

Sunshine

In Grand River, the average sunshine in September is 9.4h.

UV index

The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for average individuals.
Note: The daily high UV index of 4 in September translates into this advice:
Safety measures are advised. Light-skinned individuals may experience burns in under half an hour. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
Updated: Aug 14, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the temperature in September?

The high-temperature during September is 76.1°F (24.5°C) and the low-temperature is 56.3°F (13.5°C). The average heat index (a.k.a. 'real feel', 'feels like'), which takes the relative humidity and factors it into the air temperature reading, in August is computed to be 87.8°F (31°C).

What is the average humidity in September?

In Grand River, the average relative humidity in September is 77%.

How much does it rain in September?

In Grand River, in September, it is raining for 11.5 days, with typically 2.24" (57mm) of accumulated precipitation.

When it does not snow?

In Grand River, snow does not fall in June through September.

Does it snow in September?

In Grand River, in September, it doesn't snow. In October, it regularly snows.

How many hours of daylight does Grand River have in September?

The average day length in September is 12h and 27min.

When is the sunrise / sunset in September?

On the first day of September in Grand River, sunrise is at 6:43 am and sunset at 7:47 pm. On the last day of the month, sunrise is at 7:12 am and sunset at 6:58 pm CDT.

How many hours of sunshine does Grand River have in September?

In Grand River, the average sunshine duration in September is 9.4h.

What is the UV index intensity in September?

In Grand River, the average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium hazard to health from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Grand River, IA

Average temperature in September - Grand River, IA
  • Average high temperature in September: 76.1°F

The warmest month (with the highest average high temperature) is July (83.5°F).
The month with the lowest average high temperature is January (30.6°F).

  • Average low temperature in September: 56.3°F

The month with the highest average low temperature is July (66°F).
The coldest month (with the lowest average low temperature) is January (16.9°F).

Average pressure in September
Grand River, IA

Average pressure in September - Grand River, IA
  • Average pressure in September: 30.01"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
Grand River, IA

Average wind speed in September - Grand River, IA
  • Average wind speed in September: 7.9mph

The windiest months (with the highest average wind speed) are January, February and March (10.4mph).
The calmest months (with the lowest average wind speed) are July and August (6.9mph).

Average humidity in September
Grand River, IA

Average humidity in September - Grand River, 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
Grand River, IA

Average rainfall in September - Grand River, IA
  • Average rainfall in September: 2.24"

The wettest month (with the highest rainfall) is June (3.43").
The driest months (with the least rainfall) are January and December (0.67").

Average rainfall days in September
Grand River, IA

Average rainfall days in September - Grand River, IA
  • Average rainfall days in September: 11.5 days

The month with the highest number of rainy days is June (17.3 days).
The month with the least rainy days is January (4.8 days).

Average snowfall in September
Grand River, IA

Average snowfall in September - Grand River, IA
  • Average snowfall in September: 0"

The month with the highest snowfall is January (2.72").
The months with the least snowfall are June, July, August and September (0").

Average snowfall days in September
Grand River, IA

Average snowfall days in September - Grand River, IA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (8.6 days).
The months with the least snowfall days are June, July, August and September (0 days).

Average daylight in September /
Average sunshine in September
Grand River, IA

Average daylight in September / Average sunshine in September - Grand River, IA
  • Average daylight in September: 12h and 3min

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 2min

The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 24min).

Average sunshine days in September
Grand River, IA

Average sunshine days in September - Grand River, IA
  • Average sunshine days in September: 16 days

The month with the most sunshine days is December (20.3 days).
The month with the least sunshine days is June (8.9 days).

Average UV index in September
Grand River, IA

Average UV index in September - Grand River, 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
Grand River, IA

Average cloud cover in September - Grand River, IA
  • Average cloud cover in September: 29

The month with the most cloud cover is January (Cloud cover 51).
The month with the least cloud cover is July (Cloud cover 28).

Average visibility in September
Grand River, IA

Average visibility in September - Grand River, IA
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

Grand River, Iowa, USA

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