In April, O'Fallon typically sees daytime highs of 19.7°C and overnight lows around 6.7°C. Compared to the annual average high of 18.9°C, April runs +0.9°C.
April in O'Fallon averages a daytime high of 19.7°C and an overnight low of 6.7°C.
April runs +0.9°C compared to O'Fallon's annual average high of 18.9°C, ranking #7 of 12 months by warmth.
Plan for daytime highs near 19.7°C and cooler evenings around 6.7°C.