September weather forecast
Harrisburg, IL

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Weather in September

September in Harrisburg, Illinois marks the transition from Summer to Autumn, with temperatures fluctuating between 60.4°F (15.8°C) and 80.8°F (27.1°C). A noticeable relief from the high summer temperatures, September brings along cooler days and nights. The city undergoes a transformation with an assortment of colors, as leaves begin to turn. With rainfall drop to 1.57" (40mm), the lowest for the year, compared to the previous months, this month offers a comfortable balance of weather conditions. Gradually, the temperature keeps decreasing, setting the tone for the forthcoming Fall season.

Temperature

September's average high-temperature stands at a still moderately hot 80.8°F (27.1°C), showing little deviation from August's 85.6°F (29.8°C). During the month of September, Harrisburg experiences a steady low-temperature average of 60.4°F (15.8°C).

Heat index

September's mean heat index is evaluated at 84.2°F (29°C). Extended exposure and activity might lead to tiredness, potentially resulting in heat cramps.
Research indicates the heat index considers values in shaded locales and with light winds. Direct exposure to sunlight could raise the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', offers an insight into how hot it feels when we factor in moisture content. A person's impression of weather can be shaped by many aspects, among them metabolic variations, pregnancy, and levels of physical activity. Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Typically, children face more danger than adults as they usually perspire less. Their larger skin surface relative to their small bodies and increased heat output from their activities enhance their risk.

Humidity

In Harrisburg, the average relative humidity in September is 73%.

Rainfall

The month with the least rainfall in Harrisburg is September, when the rain falls for 10.5 days and typically collects 1.57" (40mm) of precipitation.

Snowfall

May through September are months without snowfall.

Daylight

In September, the average length of the day is 12h and 25min.
On the first day of the month, sunrise is at 6:24 am and sunset at 7:22 pm. On the last day of September, in Harrisburg, sunrise is at 6:49 am and sunset at 6:38 pm CDT.

Sunshine

The average sunshine in September is 9.2h.

UV index

In September, the average daily maximum UV index in Harrisburg is 5. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV rays for the ordinary person.
Note: In September, an average UV index of 5 transforms into the following instructions:
Safety measures are advised. Light-skinned individuals may experience burns in under half an hour. The best time to avoid the Sun's harmful UV radiation is during midday when it's most potent. Sunglasses that ward off UVA and UVB rays play a pivotal role in reducing solar eye damage.
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Frequently asked questions

What is the usual temperature for Harrisburg in September?

During September, Harrisburg experiences an average high-temperature of 80.8°F (27.1°C) and a low-temperature of 60.4°F (15.8°C). In September, the average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which combines air temperature and relative humidity, is evaluated at 84.2°F (29°C).

What is the average humidity in September in Harrisburg?

In September, the average relative humidity in Harrisburg, Illinois, is 73%.

What is the driest month in Harrisburg?

September is the month with the least rainfall. Rain falls for 10.5 days and accumulates 1.57" (40mm) of precipitation.

How much does it rain in Harrisburg in September?

In Harrisburg, during September, the rain falls for 10.5 days and regularly aggregates up to 1.57" (40mm) of precipitation.

When it does not snow in Harrisburg?

In Harrisburg, Illinois, snow does not fall in May through September.

Does it snow in Harrisburg in September?

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

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

In September, the average day length is 12h and 25min.

When is the sunrise / sunset in September in Harrisburg?

In September, on the first day of the month, sunrise is at 6:24 am and sunset at 7:22 pm. On the last day of the month, in Harrisburg, Illinois, sunrise is at 6:49 am and sunset at 6:38 pm CDT.

How many hours of sunshine does Harrisburg have in September?

In September, the average sunshine duration is 9.2h.

How high is the UV index in September in Harrisburg?

In September, the average daily maximum UV index in Harrisburg, Illinois, is 5. A UV Index of 3 to 5 symbolizes a moderate health threat 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
Harrisburg, IL

Average temperature in September - Harrisburg, IL
  • Average high temperature in September: 80.8°F

The warmest month (with the highest average high temperature) is July (87.3°F).
The month with the lowest average high temperature is January (39.7°F).

  • Average low temperature in September: 60.4°F

The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (26.2°F).

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Average pressure in September
Harrisburg, IL

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

The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).

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Average wind speed in September
Harrisburg, IL

Average wind speed in September - Harrisburg, IL
  • Average wind speed in September: 6.4mph

The windiest months (with the highest average wind speed) are January and February (9.4mph).
The calmest months (with the lowest average wind speed) are July and August (5.8mph).

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Average humidity in September
Harrisburg, IL

Average humidity in September - Harrisburg, IL
  • Average humidity in September: 73%

The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in September
Harrisburg, IL

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

The wettest month (with the highest rainfall) is April (4.8").
The driest month (with the least rainfall) is September (1.57").

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Average rainfall days in September
Harrisburg, IL

Average rainfall days in September - Harrisburg, IL
  • Average rainfall days in September: 10.5 days

The month with the highest number of rainy days is May (18.5 days).
The month with the least rainy days is November (9.7 days).

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Average snowfall in September
Harrisburg, IL

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

The month with the highest snowfall is January (1.73").
The months with the least snowfall are May, June, July, August and September (0").

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Average snowfall days in September
Harrisburg, IL

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

The month with the highest number of snowfall days is January (5.3 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
Harrisburg, IL

Average daylight in September / Average sunshine in September - Harrisburg, IL
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).

  • Average sunshine in September: 9h and 1min

The month with the most sunshine is June (Average sunshine: 10h and 36min).
The month with the least sunshine is January (Average sunshine: 4h and 36min).

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Average sunshine days in September
Harrisburg, IL

Average sunshine days in September - Harrisburg, IL
  • Average sunshine days in September: 17.1 days

The month with the most sunshine days is October (19.5 days).
The month with the least sunshine days is May (9.9 days).

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Average UV index in September
Harrisburg, IL

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

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

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Average cloud cover in September
Harrisburg, IL

Average cloud cover in September - Harrisburg, IL
  • Average cloud cover in September: 28

The months with the most cloud cover are January and February (Cloud cover 51).
The months with the least cloud cover are June and September (Cloud cover 28).

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Average visibility in September
Harrisburg, IL

Average visibility in September - Harrisburg, 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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Harrisburg, Illinois, USA

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