Average Weather in December in Sydney Australia
Daily high temperatures increase by 2°F, from 77°F to 79°F, rarely falling below 67°F or exceeding 90°F.
Daily low temperatures increase by 3°F, from 63°F to 67°F, rarely falling below 58°F or exceeding 71°F.
For reference, on January 25, the hottest day of the year, temperatures in Sydney typically range from 68°F to 80°F, while on July 19, the coldest day of the year, they range from 47°F to 62°F.
Average High and Low Temperature in December
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in December
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The month of December in Sydney experiences decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 37% to 29%. The lowest chance of overcast or mostly cloudy conditions is 29% on December 30.
The clearest day of the month is December 30, with clear, mostly clear, or partly cloudy conditions 71% of the time.
For reference, on November 22, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 38%, while on August 13, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 80%.
Cloud Cover Categories in December
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Sydney, the chance of a wet day over the course of December is decreasing, starting the month at 28% and ending it at 22%.
For reference, the year's highest daily chance of a wet day is 30% on January 31, and its lowest chance is 16% on August 13.
Probability of Precipitation in December
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during December in Sydney is gradually decreasing, starting the month at 2.8 inches, when it rarely exceeds 5.4 inches or falls below 0.7 inches, and ending the month at 2.5 inches, when it rarely exceeds 4.6 inches or falls below 0.7 inches.
The lowest average 31-day accumulation is 2.4 inches on December 23.
Average Monthly Rainfall in December
Over the course of December in Sydney, the length of the day is essentially constant. The shortest day of the month is December 1, with 14 hours, 14 minutes of daylight and the longest day is December 21, with 14 hours, 25 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Sydney is 5:36 AM on December 5 and the latest sunrise is 10 minutes later at 5:46 AM on December 31.
The earliest sunset is 7:51 PM on December 1 and the latest sunset is 18 minutes later at 8:09 PM on December 31.
Daylight saving time is observed in Sydney during 2021, but it neither starts nor ends during December, so the entire month is in daylight saving time.
For reference, on December 21, the longest day of the year, the Sun rises at 5:40 AM and sets 14 hours, 25 minutes later, at 8:05 PM, while on June 21, the shortest day of the year, it rises at 6:59 AM and sets 9 hours, 54 minutes later, at 4:53 PM.
Sunrise & Sunset with Twilight in December
The figure below presents a compact representation of key lunar data for December 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in December
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
The chance that a given day will be muggy in Sydney is rapidly increasing during December, rising from 11% to 24% over the course of the month.
For reference, on February 5, the muggiest day of the year, there are muggy conditions 41% of the time, while on June 8, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in December
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed in Sydney is essentially constant during December, remaining within 0.1 miles per hour of 7.9 miles per hour throughout.
For reference, on August 2, the windiest day of the year, the daily average wind speed is 8.2 miles per hour, while on April 8, the calmest day of the year, the daily average wind speed is 7.3 miles per hour.
The lowest daily average wind speed during December is 7.8 miles per hour on December 10.
Average Wind Speed in December
The hourly average wind direction in Sydney throughout December is predominantly from the east, with a peak proportion of 39% on December 31.
Wind Direction in December
Sydney is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature in Sydney is gradually increasing during December, rising by 3°F, from 69°F to 72°F, over the course of the month.
Average Water Temperature in December
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
Temperatures in Sydney are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in December
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
The average accumulated growing degree days in Sydney are rapidly increasing during December, increasing by 625°F, from 1,724°F to 2,349°F, over the course of the month.
Growing Degree Days in December
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy in Sydney is essentially constant during December, remaining within 0.2 kWh of 7.5 kWh throughout.
The highest average daily incident shortwave solar energy during December is 7.8 kWh on December 31.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Sydney are -33.868 deg latitude, 151.207 deg longitude, and 190 ft elevation.
The topography within 2 miles of Sydney contains only modest variations in elevation, with a maximum elevation change of 387 feet and an average elevation above sea level of 69 feet. Within 10 miles contains only modest variations in elevation (728 feet). Within 50 miles contains significant variations in elevation (3,232 feet).
The area within 2 miles of Sydney is covered by artificial surfaces (54%), water (29%), and sparse vegetation (12%), within 10 miles by artificial surfaces (38%) and water (35%), and within 50 miles by water (50%) and trees (38%).
This report illustrates the typical weather in Sydney, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Sydney.
For each station, the records are corrected for the elevation difference between that station and Sydney according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Sydney is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Sydney and a given station.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for airports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.