In December, Diamond Bar typically sees daytime highs of 18.3°C and overnight lows around 5.6°C. Compared to the annual average high of 24.1°C, December runs -5.9°C.
December in Diamond Bar averages a daytime high of 18.3°C and an overnight low of 5.6°C.
December runs -5.9°C compared to Diamond Bar's annual average high of 24.1°C, ranking #11 of 12 months by warmth.
Plan for daytime highs near 18.3°C and cooler evenings around 5.6°C.