September weather forecast
Waterloo, IA

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Weather in September

With the end of summer, September in Waterloo comes with more moderate temperatures and the first hints of fall. An unmistakable onset of the autumn season is experienced this month as the landscape begins to transform. The average high temperature drops to 73.2°F (22.9°C), a noticeable decrease from August. Outdoor activities continue to be common as Waterloo residents seek to take advantage of the agreeable weather. Despite the changing scenario, the city benefits from long sunlight hours.

Temperature

Waterloo's progression into September involves a gentle drop in the average high-temperature, from a moderately hot 78.6°F (25.9°C) in August to a pleasant 73.2°F (22.9°C). Waterloo observes an average nighttime low-temperature of 54.5°F (12.5°C) during the month of September.

Humidity

In September, the average relative humidity is 78%.

Rainfall

In Waterloo, in September, it is raining for 11.2 days, with typically 2.48" (63mm) of accumulated precipitation. Throughout the year, in Waterloo, Iowa, there are 133.6 rainfall days, and 28.27" (718mm) of precipitation is accumulated.

Snowfall

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

Daylight

The average length of the day in September in Waterloo, Iowa, is 12h and 28min.
On the first day of the month, sunrise is at 6:35 am and sunset at 7:43 pm. On the last day of September, in Waterloo, sunrise is at 7:06 am and sunset at 6:51 pm CDT.

Sunshine

In September, the average sunshine in Waterloo is 9.1h.

UV index

In Waterloo, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV rays for the ordinary person.
Note: In September, the average maximum UV index of 4 translates into the following recommendations:
Act with care - The need to guard against sun damage is communicated. To prevent harmful UV exposure, minimize direct contact with the Sun around midday. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key.
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Frequently asked questions

What is the usual temperature for Waterloo in September?

September temperatures in Waterloo vary between a high-temperature of 73.2°F (22.9°C) and a low-temperature of 54.5°F (12.5°C).

What is the average humidity in September in Waterloo?

In Waterloo, the average relative humidity in September is 78%.

How many days does it rain in September in Waterloo?

In Waterloo, Iowa, in September, it is raining for 11.2 days, with typically 2.48" (63mm) of accumulated precipitation.

When it does not snow in Waterloo?

June through September are months without snowfall in Waterloo.

Does it snow in Waterloo in September?

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

What is the average length of the day in September in Waterloo?

The average day length in September in Waterloo is 12h and 28min.

When are sunrise and sunset in September in Waterloo?

On the first day of September in Waterloo, Iowa, sunrise is at 6:35 am and sunset at 7:43 pm. On the last day of the month, sunrise is at 7:06 am and sunset at 6:51 pm CDT.

How many hours of sunshine does Waterloo have in September?

In September, the average sunshine duration is 9.1h.

How high is the UV index in September in Waterloo?

In Waterloo, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate health threat from unprotected exposure to UV radiation.
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
Waterloo, IA

Average temperature in September - Waterloo, IA
  • Average high temperature in September: 73.2°F

The warmest month (with the highest average high temperature) is July (80.1°F).
The month with the lowest average high temperature is January (24.3°F).

  • Average low temperature in September: 54.5°F

The month with the highest average low temperature is July (63.1°F).
The coldest month (with the lowest average low temperature) is January (12°F).

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Average pressure in September
Waterloo, IA

Average pressure in September - Waterloo, 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).

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Average wind speed in September
Waterloo, IA

Average wind speed in September - Waterloo, IA
  • Average wind speed in September: 8.2mph

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).

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Average humidity in September
Waterloo, IA

Average humidity in September - Waterloo, IA
  • Average humidity in September: 78%

The month with the highest relative humidity is January (87%).
The month with the lowest relative humidity is October (72%).

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Average rainfall in September
Waterloo, IA

Average rainfall in September - Waterloo, IA
  • Average rainfall in September: 2.48"

The wettest month (with the highest rainfall) is June (4.29").
The driest months (with the least rainfall) are January and February (1.02").

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Average rainfall days in September
Waterloo, IA

Average rainfall days in September - Waterloo, IA
  • Average rainfall days in September: 11.2 days

The month with the highest number of rainy days is June (18.1 days).
The month with the least rainy days is February (4 days).

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Average snowfall in September
Waterloo, IA

Average snowfall in September - Waterloo, IA
  • Average snowfall in September: 0"

The month with the highest snowfall is January (4.21").
The months with the least snowfall are June, July, August and September (0").

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Average snowfall days in September
Waterloo, IA

Average snowfall days in September - Waterloo, IA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (11.5 days).
The months with the least snowfall days are June, July, August and September (0 days).

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Average daylight in September /
Average sunshine in September
Waterloo, IA

Average daylight in September / Average sunshine in September - Waterloo, 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 6min).

  • 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: 3h and 48min).

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Average sunshine days in September
Waterloo, IA

Average sunshine days in September - Waterloo, IA
  • Average sunshine days in September: 16.5 days

The month with the most sunshine days is October (17.8 days).
The month with the least sunshine days is June (10 days).

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Average UV index in September
Waterloo, IA

Average UV index in September - Waterloo, IA
  • Average UV index in September: 4

The month with the highest UV index is June (UV index 6).
The month with the lowest UV index is December (UV index 1).

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Average cloud cover in September
Waterloo, IA

Average cloud cover in September - Waterloo, IA
  • Average cloud cover in September: 32

The month with the most cloud cover is January (Cloud cover 60).
The month with the least cloud cover is August (Cloud cover 31).

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Average visibility in September
Waterloo, IA

Average visibility in September - Waterloo, IA
  • Average visibility in September: 6mi

The months with the highest visibility are February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are January, July and August (5mi).

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Waterloo, Iowa, USA

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