Warm
Average highs sit around 26°C, giving warm days by monthly-average standards.
September verdict
O'Fallon, Illinois, United States in September
Weather score70Very good
Very good for holiday weather
Average highs sit around 26°C, giving warm days by monthly-average standards. Sunshine averages 7.9h per day, enough for a balanced month. Rainfall averages 81mm, so some wet days are possible.
September weather
Monthly averages
Temp
26°C
Rain
81mm
Sun
7.9h
Weather score
70
Very good
Seasonal climate calendar
TemperatureTemp
RainRain
SunSun
Weather scoreWeather score
Trip feel
Showers
Rainfall averages 81mm, so some wet days are possible.
Some sun
Sunshine averages 7.9h per day, enough for a balanced month.
Map
Weather map
Compare O'Fallon, Illinois, United States with nearby places by weather score, rain, sun, temperature, and swim conditions.
Temperature
September26°C average high
September sits in the warmer part of the year, so midday sightseeing can feel heavier than in cooler months.
Warmest monthsMay to September
This stretch sets the upper range for average daytime heat.
Rain
September81mm average rain
September sits near O'Fallon's yearly rainfall average, so rain is a normal planning factor rather than an outlier.
Driest monthsJanuary to February and October to December
This is the drier part of the year, when outdoor plans usually need less weather flexibility.
Sun
September7.9 hours average sun
September sits close to O'Fallon's yearly sunshine average, so it is a middle-of-the-pack month for bright days.
Brightest monthsMay to August
This stretch has the strongest sunshine in the monthly averages.
Weather score
September70 weather score
September scores above O'Fallon's yearly average, so the overall weather mix is stronger than most months.
Best weather monthsJune to September
These months have the strongest weather score in the monthly averages.
