September weather forecast
Washington, IL

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Weather in September

The first month of the autumn, September, is still a warm month in Washington, Illinois, with an average temperature fluctuating between 57.2°F (14°C) and 76.1°F (24.5°C).

Temperature

The advent of September presents an average high-temperature of a still warm 76.1°F (24.5°C), maintaining a close correlation with the preceding month. In Washington, an average nighttime temperature of 57.2°F (14°C) is expected during September.

Humidity

In Washington, the average relative humidity in September is 76%.

Rainfall

In Washington, Illinois, during September, the rain falls for 11.2 days and regularly aggregates up to 1.57" (40mm) of precipitation. Throughout the year, there are 128.3 rainfall days, and 19.13" (486mm) of precipitation is accumulated.

Snowfall

May through October are months without snowfall in Washington, Illinois.

Daylight

The average length of the day in September is 12h and 27min.
On the first day of September in Washington, Illinois, sunrise is at 6:25 am and sunset at 7:29 pm. On the last day of the month, sunrise is at 6:53 am and sunset at 6:40 pm CDT.

Sunshine

In Washington, the average sunshine in September is 9.2h.

UV index

In September, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for the average person.
Note: In September, a daily UV index of 5 turns into the following recommendations:
Undertake protective steps - Obligation to safeguard skin and eyes from harm is in place. Direct exposure to the Sun during its peak hours around mid-day should be minimized for safety. Safeguard your eyes, ears, and face from sun rays with the aid of a wide-brim hat.
Updated: Feb 12, 2024 | Published by: Weather U.S. | Resources

Frequently asked questions

What is the usual temperature for Washington in September?

Washington in September has an average high-temperature of 76.1°F (24.5°C) and an average low-temperature of 57.2°F (14°C). The average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which factors the actual air temperature with the relative humidity, in August is calculated to be 86°F (30°C).

What is the average humidity in September in Washington?

In September, the average relative humidity is 76%.

How much does it rain in Washington in September?

In Washington, in September, it is raining for 11.2 days, with typically 1.57" (40mm) of accumulated precipitation.

When it does not snow in Washington?

May through October are months without snowfall in Washington, Illinois.

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

In Washington, the average day length in September is 12h and 27min.

When are sunrise and sunset in September in Washington?

In September, on the first day of the month, sunrise is at 6:25 am and sunset at 7:29 pm. On the last day of the month, sunrise is at 6:53 am and sunset at 6:40 pm CDT.

How long on average sun shines in September in Washington?

In September, the average sunshine duration in Washington is 9.2h.

What is the UV index intensity in September in Washington?

In September, the average daily maximum UV index in Washington, Illinois, is 5. A UV Index of 3 to 5 symbolizes a medium hazard to health from exposure to the Sun's 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
Washington, IL

Average temperature in September - Washington, IL
  • Average high temperature in September: 76.1°F

The warmest month (with the highest average high temperature) is July (81.5°F).
The month with the lowest average high temperature is January (30.6°F).

  • Average low temperature in September: 57.2°F

The month with the highest average low temperature is July (64.9°F).
The coldest month (with the lowest average low temperature) is January (18.5°F).

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Average pressure in September
Washington, IL

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

The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).

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Average wind speed in September
Washington, IL

Average wind speed in September - Washington, IL
  • Average wind speed in September: 7.6mph

The windiest month (with the highest average wind speed) is April (10.6mph).
The calmest month (with the lowest average wind speed) is August (6.5mph).

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Average humidity in September
Washington, IL

Average humidity in September - Washington, IL
  • Average humidity in September: 76%

The month with the highest relative humidity is July (84%).
The month with the lowest relative humidity is October (71%).

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Average rainfall in September
Washington, IL

Average rainfall in September - Washington, IL
  • Average rainfall in September: 1.57"

The wettest month (with the highest rainfall) is May (2.6").
The driest month (with the least rainfall) is November (0.94").

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Average rainfall days in September
Washington, IL

Average rainfall days in September - Washington, IL
  • Average rainfall days in September: 11.2 days

The month with the highest number of rainy days is July (16.4 days).
The month with the least rainy days is January (4.4 days).

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Average snowfall in September
Washington, IL

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

The month with the highest snowfall is January (2.68").
The months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in September
Washington, IL

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

The month with the highest number of snowfall days is January (10.3 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
Washington, IL

Average daylight in September / Average sunshine in September - Washington, IL
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 18min).

  • Average sunshine in September: 9h and 1min

The month with the most sunshine is June (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 3h and 54min).

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Average sunshine days in September
Washington, IL

Average sunshine days in September - Washington, IL
  • Average sunshine days in September: 17.2 days

The month with the most sunshine days is December (20.5 days).
The month with the least sunshine days is July (11.4 days).

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Average UV index in September
Washington, IL

Average UV index in September - Washington, IL
  • Average UV index in September: 5

The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in September
Washington, IL

Average cloud cover in September - Washington, IL
  • Average cloud cover in September: 30

The month with the most cloud cover is January (Cloud cover 58).
The month with the least cloud cover is September (Cloud cover 30).

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Average visibility in September
Washington, IL

Average visibility in September - Washington, IL
  • 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).

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Washington, Illinois, USA

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