O'Fallon Weather in September
O'Fallon in September sees high temperatures, with highs around 27°C (81°F) and overnight lows of 15°C (59°F). Rainfall is fairly high at around 102 mm (4 in) on average, so pack waterproofs just in case.
Rainfall in O'Fallon in September
Typically, about 10 days will experience rainfall, with an average of 102 mm (4 in) for the month. The rain this month tends to fall in heavier spells rather than light drizzle. When it rains, showers can be significant.
Temperature in O'Fallon in September
Temperatures in O'Fallon in September top out at 27°C (81°F) and drop to 15°C (59°F) overnight. This gives the month a fairly typical daily rhythm, with warmer afternoons and more comfortable nights. At 15°C (59°F) overnight, it can feel quite a bit cooler after dark. Worth packing something warmer for evenings, but the cooler temperatures are ideal for sleeping.
Sunshine in O'Fallon in September
The city usually sees around 235 hours of sunlight, indicating many sunny days — a great month for sightseeing.If you prefer dry days with pleasant temperatures, October typically offers the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our O'Fallon's climate page.
O'Fallon Temperature in September
Min Temperature
15°C (59°F)
Max Temperature
27°C (81°F)
Chance of Rain
33%
Precipitation
102 mm (4 in)
Rainy days
10 days
Humidity
71% *
Sunshine
235 hours *
Percentage Sunshine
63% *
Best Places in the United States of America in September
Find out more about the weather in the United States of America and which places have the best travel conditions in this month. See all of the United States of America in September →
perfect weather
pleasant
tolerable
unpleasant
poor
What to Wear in O'Fallon in September
Warm but pleasant conditions in O'Fallon in September. Focus on lightweight, maybe with natural fabrics, cotton blend shirts, comfortable shorts, and breathable footwear. A light cover-up for sun protection is smart too. Expect heavy rainfall, so bring good rain protection and waterproof bags. Don't forget sun protection, sunglasses, sunscreen, and a hat. These are all good ideas with this much sunshine.What To Do in O'Fallon in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our O'Fallon's climate page.
Temperature Rainfall Sunshine Humidity
See the full O'Fallon climate overview or explore weather in the United States of America.
