In May, Saint Charles typically sees daytime highs of 24.6°C and overnight lows around 12.2°C. Compared to the annual average high of 18.7°C, May runs +5.9°C.
May in Saint Charles averages a daytime high of 24.6°C and an overnight low of 12.2°C.
May runs +5.9°C compared to Saint Charles's annual average high of 18.7°C, ranking #5 of 12 months by warmth.
Plan for daytime highs near 24.6°C and cooler evenings around 12.2°C.