In December, Simi Valley typically sees daytime highs of 17.0°C and overnight lows around 5.1°C. Compared to the annual average high of 22.3°C, December runs -5.3°C.
December in Simi Valley averages a daytime high of 17.0°C and an overnight low of 5.1°C.
December runs -5.3°C compared to Simi Valley's annual average high of 22.3°C, ranking #11 of 12 months by warmth.
Plan for daytime highs near 17.0°C and cooler evenings around 5.1°C.