A series of tables gives December data by year for temperature and precipitation. Sea Temperature 21 °C 70 °F. Temperature 22 °C 72 °F. Climate in Sydney in december. Low Temperature 18 °C 64 °F. December. Average high temperature in December: 24.2°C; The warmest month (with the highest average high temperature) is January (25.9°C). Sunshine Hours 10 hrs. Rainfall in December was above average in the State's northwest and … High Temperature 26 °C 79 °F. The climate quite comfortable in this location in december. Sydney Weather December Averages, Australia. Overall, it was the State's second-warmest December on record. December temperatures were above average throughout South Australia, with large areas of the State very much warmer than average for both daytime and night time temperatures. High Temperature 24 °C 75 °F. This is a great time to enjoy Sydney’s abundant beaches when water temperatures rise to 21.9 - 23.7°C (71.4 - 74.7°F). South Australia in December 2018: very warm; drier than average in many districts. Australia heatwave to break Christmas weather records with temperatures up to 47C forecast This article is more than 1 year old. In december, maximum temperature is 81°F and minimum temperature is 72°F (for an average temperature of 76°F). Average low temperature in December: 13°C; The month with the highest average low temperature is February (14.6°C). December. Sunshine Hours 9 hrs. December temperatures were above average throughout South Australia, with large areas of the State very much warmer than average for both daytime and night time temperatures. Plan ahead with this information on temperature and rainfall. Calendars – online and print friendly – for any year and month Weather reports from January 2018 in Melbourne, Victoria, Australia with highs and lows Overall, it was the State's second-warmest December on record. With December ushering in the first days of Australia’s summer, the weather within all areas is quite warm. Rainfall days 14 days. Australia December 2018 – Calendar with holidays. South Australia in December 2018: very warm; drier than average in many districts. The month with the lowest average high temperature is July (13.5°C). Nevertheless on December 25 all Australians like the rest of Catholics celebrate Christmas and January 26 is the celebration of Australia’s Day. With December ushering in the first days of Australia’s summer, the weather within all areas is quite warm. Monthly calendar for the month December in year 2018. Summer (December – February) During summer, average temperatures range from 18.6 - 25.8°C (65.5 - 78.4°F), and average humidity spikes to 65%.