In December, Fullerton typically sees daytime highs of 19.4°C and overnight lows around 6.8°C. Compared to the annual average high of 23.9°C, December runs -4.5°C.
December in Fullerton averages a daytime high of 19.4°C and an overnight low of 6.8°C.
December runs -4.5°C compared to Fullerton's annual average high of 23.9°C, ranking #11 of 12 months by warmth.
Plan for daytime highs near 19.4°C and cooler evenings around 6.8°C.