September weather forecast
Mount Prospect, IL

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Weather in September

September signifies the start of the fall season in Mount Prospect, with a noticeable decrease in temperature. With no snowfall recorded, the weather is still warm without the scorching summer heat. With the advent of fall, the city begins to detox from the summer’s intense humidity. The September weather in Mount Prospect is marked with beautiful sunsets, falling leaves and an overall sense of calming change. The pleasant and moderate temperatures make September a delightful time to relish the outdoor beauty of Mount Prospect.

Temperature

In Mount Prospect, entering September brings a subtle temperature decrement, reducing from August's moderately hot 79.7°F (26.5°C) to an agreeable 73.2°F (22.9°C). The average temperature in Mount Prospect, Illinois, drops to a refreshing 58.8°F (14.9°C) during the night in the month of September.

Humidity

In Mount Prospect, the average relative humidity in September is 74%.

Rainfall

In September, the rain falls for 13.2 days. Throughout September, 2.24" (57mm) of precipitation is accumulated. In Mount Prospect, during the entire year, the rain falls for 153.3 days and collects up to 30.12" (765mm) of precipitation.

Snowfall

June through September are months without snowfall.

Daylight

In Mount Prospect, Illinois, the average length of the day in September is 12h and 28min.
On the first day of the month, sunrise is at 6:18 am and sunset at 7:24 pm. On the last day of September, sunrise is at 6:48 am and sunset at 6:34 pm CDT.

Sunshine

In Mount Prospect, the average sunshine in September is 8.8h.

UV index

In Mount Prospect, the average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a medium health hazard from unsafe exposure to UV radiation for ordinary individuals.
Note: In September, an average UV index of 4 transforms into the following instructions:
Take necessary precautions - Defending against sun damage is advocated. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. Sunglasses that guard against UVA and UVB rays are pivotal in minimizing sun-induced ocular damage.
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Frequently asked questions

What are the temperatures in Mount Prospect in September?

In September, in Mount Prospect, the average high-temperature is 73.2°F (22.9°C), and the average low-temperature is 58.8°F (14.9°C). The average heat index (a.k.a. 'apparent temperature', 'real feel'), which represents the influence of relative humidity on air temperature, in July is computed to be 86°F (30°C).

What is the average humidity in September in Mount Prospect?

In September, the average relative humidity in Mount Prospect is 74%.

How much does it rain in Mount Prospect in September?

In Mount Prospect, Illinois, in September, it is raining for 13.2 days, with typically 2.24" (57mm) of accumulated precipitation.

When it does not snow in Mount Prospect?

In Mount Prospect, Illinois, snow does not fall in June through September.

Does it snow in Mount Prospect in September?

In Mount Prospect, Illinois, in September, it doesn't snow. In October, it regularly snows.

What is the average length of the day in September in Mount Prospect?

In September, the average day length in Mount Prospect is 12h and 28min.

What time are sunrise and sunset in September in Mount Prospect?

On the first day of September in Mount Prospect, sunrise is at 6:18 am and sunset at 7:24 pm. On the last day of the month, sunrise is at 6:48 am and sunset at 6:34 pm CDT.

How long on average sun shines in September in Mount Prospect?

In September, the average sunshine duration is 8.8h.

How high is the UV index in September in Mount Prospect?

In September, the average daily maximum UV index in Mount Prospect, Illinois, is 4. A UV Index 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
Mount Prospect, IL

Average temperature in September - Mount Prospect, IL
  • Average high temperature in September: 73.2°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 (28.2°F).

  • Average low temperature in September: 58.8°F

The month with the highest average low temperature is July (66.4°F).
The coldest month (with the lowest average low temperature) is January (18°F).

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Average pressure in September
Mount Prospect, IL

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

The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in September
Mount Prospect, IL

Average wind speed in September - Mount Prospect, IL
  • Average wind speed in September: 7.7mph

The windiest month (with the highest average wind speed) is January (10.4mph).
The calmest month (with the lowest average wind speed) is August (6.5mph).

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Average humidity in September
Mount Prospect, IL

Average humidity in September - Mount Prospect, IL
  • Average humidity in September: 74%

The months with the highest relative humidity are January and February (82%).
The month with the lowest relative humidity is October (72%).

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Average rainfall in September
Mount Prospect, IL

Average rainfall in September - Mount Prospect, IL
  • Average rainfall in September: 2.24"

The wettest month (with the highest rainfall) is May (3.9").
The driest month (with the least rainfall) is December (1.46").

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Average rainfall days in September
Mount Prospect, IL

Average rainfall days in September - Mount Prospect, IL
  • Average rainfall days in September: 13.2 days

The month with the highest number of rainy days is May (18 days).
The month with the least rainy days is February (5.6 days).

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Average snowfall in September
Mount Prospect, IL

Average snowfall in September - Mount Prospect, IL
  • Average snowfall in September: 0"

The month with the highest snowfall is January (4.96").
The months with the least snowfall are June, July, August and September (0").

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Average snowfall days in September
Mount Prospect, IL

Average snowfall days in September - Mount Prospect, IL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (11.8 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
Mount Prospect, IL

Average daylight in September / Average sunshine in September - Mount Prospect, IL
  • 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: 8h and 5min

The month with the most sunshine is July (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).

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Average sunshine days in September
Mount Prospect, IL

Average sunshine days in September - Mount Prospect, IL
  • Average sunshine days in September: 14.1 days

The month with the most sunshine days is November (16.3 days).
The month with the least sunshine days is June (10.7 days).

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Average UV index in September
Mount Prospect, IL

Average UV index in September - Mount Prospect, IL
  • 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 December (UV index 1).

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Average cloud cover in September
Mount Prospect, IL

Average cloud cover in September - Mount Prospect, IL
  • Average cloud cover in September: 31

The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 29).

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Average visibility in September
Mount Prospect, IL

Average visibility in September - Mount Prospect, IL
  • 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).

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Mount Prospect, Illinois, USA

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