September weather forecast
Ottawa, IL

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Weather in September

The first month of the autumn, September, is also a moderately hot month in Ottawa, Illinois, with temperature in the range of an average low of 56.1°F (13.4°C) and an average high of 74.5°F (23.6°C).

Temperature

As September unfolds, the average high-temperature reaches a still warm 74.5°F (23.6°C), hinting at a slight fluctuation from the previous month. September witnesses an average nighttime temperature of 56.1°F (13.4°C).

Humidity

The average relative humidity in September is 78%.

Rainfall

In Ottawa, during September, the rain falls for 13.4 days and regularly aggregates up to 2.52" (64mm) of precipitation. Throughout the year, there are 166.3 rainfall days, and 35.35" (898mm) of precipitation is accumulated.

Snowfall

May through September are months without snowfall in Ottawa.

Daylight

The average length of the day in September in Ottawa is 12h and 28min.
On the first day of September in Ottawa, sunrise is at 6:22 am and sunset at 7:27 pm. On the last day of the month, sunrise is at 6:51 am and sunset at 6:38 pm CDT.

Sunshine

The average sunshine in September is 8.9h.

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 unprotected exposure to Sun's UV rays for ordinary individuals.
Note: In September, a daily UV index of 4 turns into the following recommendations:
Prioritize safety - Recommendations to avert sunburn are shared. Direct Sun exposure should be minimized especially during midday when radiation is most intense. Tightly woven clothing, when worn loosely, shields effectively against the Sun.
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Frequently asked questions

What is the usual temperature for Ottawa in September?

The high-temperature, in September, in Ottawa, records 74.5°F (23.6°C), while the low-temperature is 56.1°F (13.4°C). In July, the average heat index (a.k.a. 'real feel', 'feels like'), which represents the influence of relative humidity on air temperature, is appraised at 87.8°F (31°C).

What is the average humidity in September in Ottawa?

The average relative humidity in September in Ottawa, Illinois, is 78%.

How many days does it rain in September in Ottawa?

In September, the rain falls for 13.4 days. Throughout September, 2.52" (64mm) of precipitation is accumulated.

When it does not snow in Ottawa?

May through September are months without snowfall.

Does it snow in Ottawa in September?

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

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

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

When is the sunrise / sunset in September in Ottawa?

In September, on the first day of the month, sunrise is at 6:22 am and sunset at 7:27 pm. On the last day of the month, in Ottawa, Illinois, sunrise is at 6:51 am and sunset at 6:38 pm CDT.

How many hours of sunshine does Ottawa have in September?

The average sunshine duration in September in Ottawa is 8.9h.

What is the UV index reading in September in Ottawa?

In September, the average daily maximum UV index is 4. A UV Index value of 3 to 5 symbolizes a moderate vulnerability 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
Ottawa, IL

Average temperature in September - Ottawa, IL
  • Average high temperature in September: 74.5°F

The warmest month (with the highest average high temperature) is July (81°F).
The month with the lowest average high temperature is January (29.1°F).

  • Average low temperature in September: 56.1°F

The month with the highest average low temperature is July (64.2°F).
The coldest month (with the lowest average low temperature) is January (17.2°F).

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Average pressure in September
Ottawa, IL

Average pressure in September - Ottawa, IL
  • Average pressure in September: 30.03"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in September
Ottawa, IL

Average wind speed in September - Ottawa, IL
  • Average wind speed in September: 7.3mph

The windiest month (with the highest average wind speed) is April (10.2mph).
The calmest month (with the lowest average wind speed) is August (6.2mph).

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Average humidity in September
Ottawa, IL

Average humidity in September - Ottawa, IL
  • Average humidity in September: 78%

The month with the highest relative humidity is July (85%).
The month with the lowest relative humidity is October (72%).

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Average rainfall in September
Ottawa, IL

Average rainfall in September - Ottawa, IL
  • Average rainfall in September: 2.52"

The wettest month (with the highest rainfall) is May (5").
The driest month (with the least rainfall) is November (1.81").

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Average rainfall days in September
Ottawa, IL

Average rainfall days in September - Ottawa, IL
  • Average rainfall days in September: 13.4 days

The month with the highest number of rainy days is July (19.9 days).
The month with the least rainy days is February (6.2 days).

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Average snowfall in September
Ottawa, IL

Average snowfall in September - Ottawa, IL
  • Average snowfall in September: 0"

The month with the highest snowfall is February (5.08").
The months with the least snowfall are May, June, July, August and September (0").

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Average snowfall days in September
Ottawa, IL

Average snowfall days in September - Ottawa, IL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (12.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).

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Average daylight in September /
Average sunshine in September
Ottawa, IL

Average daylight in September / Average sunshine in September - Ottawa, IL
  • 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 12min).

  • Average sunshine in September: 8h and 5min

The month with the most sunshine is June (Average sunshine: 9h and 48min).
The month with the least sunshine is January (Average sunshine: 3h and 54min).

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Average sunshine days in September
Ottawa, IL

Average sunshine days in September - Ottawa, IL
  • Average sunshine days in September: 13.2 days

The month with the most sunshine days is November (17 days).
The month with the least sunshine days is July (7.2 days).

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Average UV index in September
Ottawa, IL

Average UV index in September - Ottawa, IL
  • Average UV index in September: 4

The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January and December (UV index 1).

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Average cloud cover in September
Ottawa, IL

Average cloud cover in September - Ottawa, IL
  • Average cloud cover in September: 32

The month with the most cloud cover is January (Cloud cover 59).
The month with the least cloud cover is September (Cloud cover 32).

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Average visibility in September
Ottawa, IL

Average visibility in September - Ottawa, IL
  • Average visibility in September: 6mi

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

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Ottawa, Illinois, USA

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