In August, Saint Charles typically sees daytime highs of 30.7°C and overnight lows around 18.4°C. Compared to the annual average high of 18.7°C, August runs +12.0°C.
August in Saint Charles averages a daytime high of 30.7°C and an overnight low of 18.4°C.
August runs +12.0°C compared to Saint Charles's annual average high of 18.7°C, ranking #2 of 12 months by warmth.
Plan for daytime highs near 30.7°C and cooler evenings around 18.4°C.