In December, Rialto typically sees daytime highs of 17.4°C and overnight lows around 3.7°C. Compared to the annual average high of 24.7°C, December runs -7.3°C.
December in Rialto averages a daytime high of 17.4°C and an overnight low of 3.7°C.
December runs -7.3°C compared to Rialto's annual average high of 24.7°C, ranking #11 of 12 months by warmth.
Plan for daytime highs near 17.4°C and cooler evenings around 3.7°C.