In June, O'Fallon typically sees daytime highs of 29.4°C and overnight lows around 17.0°C. Compared to the annual average high of 18.9°C, June runs +10.6°C.
June in O'Fallon averages a daytime high of 29.4°C and an overnight low of 17.0°C.
June runs +10.6°C compared to O'Fallon's annual average high of 18.9°C, ranking #3 of 12 months by warmth.
Plan for daytime highs near 29.4°C and cooler evenings around 17.0°C.