what is the weather in allentown?
Weather in Allentown in December 2018 Guide to Allentown weather in December. The average maximum daytime temperature in Allentown in December is a cold 4Â°C (39Â°F). The average night-time temperature is usually a very cold -4Â°C (25Â°F). There are usually 4 hours of bright sunshine each day, which represents 42% of the 9 hours of daylight.