Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The onset of September brings an average high-temperature of a still warm 74.7°F (23.7°C), nearly matching the August temperature. An average minimum temperature of 56.1°F (13.4°C) is recorded in Princeton during the month of September.Humidity
In Princeton, the average relative humidity in September is 78%.Rainfall
In Princeton, in September, during 10.5 rainfall days, 1.22" (31mm) of precipitation is typically accumulated. Throughout the year, there are 130 rainfall days, and 17.64" (448mm) of precipitation is accumulated.Snowfall
In Princeton, snow does not fall in May through September.Daylight
The average length of the day in September is 12h and 28min.On the first day of September, sunrise is at 6:24 am and sunset at 7:30 pm. On the last day of the month, sunrise is at 6:54 am and sunset at 6:40 pm CDT.
Sunshine
The average sunshine in September is 8.9h.UV index
The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the average person.Note: The maximum UV index, 4 during September, leads to the following recommendations:
Undertake precautions - Obligation exists to protect against skin and eye damage. The Sun's UV radiation is especially harmful around midday, so reduce exposure and stay safe. In bright sunlight, prioritize sunglasses that grant protection from UVA and UVB radiation. Alert! The snow's reflection can amplify the UV radiation of the Sun nearly twice.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
Does it snow in September?
What is the average length of the day in September?
What time are sunrise and sunset in September?
How many hours of sunshine does Princeton have in September?
What is the UV index reading in September?
Average temperature in September
Princeton, IL
- Average high temperature in September: 74.7°F
The warmest month (with the highest average high temperature) is July (80.6°F).
The month with the lowest average high temperature is January (28.8°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 (16.5°F).
Average pressure in September
Princeton, 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 (29.91"Hg).
Average wind speed in September
Princeton, IL
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is April (10.5mph).
The calmest month (with the lowest average wind speed) is August (6.4mph).
Average humidity in September
Princeton, 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%).
Average rainfall in September
Princeton, IL
- Average rainfall in September: 1.22"
The wettest month (with the highest rainfall) is May (2.91").
The driest month (with the least rainfall) is January (0.75").
Average rainfall days in September
Princeton, IL
- Average rainfall days in September: 10.5 days
The month with the highest number of rainy days is May (17 days).
The month with the least rainy days is February (4.5 days).
Average snowfall in September
Princeton, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.09").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Princeton, IL
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is January (10.4 days).
The months with the least snowfall days are May, June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Princeton, 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 months with the most sunshine are June and July (Average sunshine: 9h and 42min).
The month with the least sunshine is January (Average sunshine: 3h and 48min).
Average sunshine days in September
Princeton, IL
- Average sunshine days in September: 17.6 days
The month with the most sunshine days is November (19.5 days).
The month with the least sunshine days is June (11.8 days).
Average UV index in September
Princeton, IL
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January and December (UV index 1).
Average cloud cover in September
Princeton, IL
- 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 September (Cloud cover 32).
Average visibility in September
Princeton, 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).
Princeton, Illinois, USA
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