In May, Castro Valley typically sees daytime highs of 21.5°C and overnight lows around 9.9°C. Compared to the annual average high of 20.0°C, May runs +1.5°C.
May in Castro Valley averages a daytime high of 21.5°C and an overnight low of 9.9°C.
May runs +1.5°C compared to Castro Valley's annual average high of 20.0°C, ranking #6 of 12 months by warmth.
Plan for daytime highs near 21.5°C and cooler evenings around 9.9°C.