In December, Janesville typically sees daytime highs of -0.1°C and overnight lows around -8.6°C. Compared to the annual average high of 13.9°C, December runs -14.0°C.
December in Janesville averages a daytime high of -0.1°C and an overnight low of -8.6°C.
December runs -14.0°C compared to Janesville's annual average high of 13.9°C, ranking #10 of 12 months by warmth.
Plan for daytime highs near -0.1°C and cooler evenings around -8.6°C.