September weather forecastOttawa, IL
September
Weather in September
September, the first month of the autumn in Ottawa, is also a moderately hot month, with an average temperature fluctuating between 74.5°F (23.6°C) and 56.1°F (13.4°C).Temperature
The transition from August to September sees an average high-temperature of a still moderately hot 74.5°F (23.6°C), indicating a minor variance from the prior month. Nighttime temperature dips to a mean of 56.1°F (13.4°C) during September.Humidity
In September, the average relative humidity is 78%.Rainfall
In Ottawa, Illinois, in September, it is raining for 13.4 days, with typically 2.52" (64mm) of accumulated 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.Daylight
The average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:22 am and sunset at 7:27 pm. On the last day of September, 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 exposure to the Sun's UV rays for ordinary individuals.Note: A daily maximum UV index of 4 in September translates into the following instructions:
Take precautions - Protection against sun damage is advised. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Loose clothes with a tight weave are optimal for safeguarding yourself against the Sun's rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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).
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).
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).
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%).
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").
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).
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").
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).
Average daylight in September /
Average sunshine in September
Ottawa, IL
- Average daylight in September: 12h and 30min
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 54min
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).
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).
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).
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).
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).
