Weather and climate in NSW
What’s special about NSW?
NSW is home to a wide range of landscapes and ecosystems. Our long coastal strip is home to most of the state’s people, we have the largest and highest alpine areas in Australia, extensive rangelands, and some of Australia’s largest and most productive agricultural areas, including large parts of the Murray-Darling Basin.
We are used to dealing with large fluctuations in temperature and rainfall. Indeed the seasonal and regional climate variability of NSW is greater than in many other parts of the world. Heatwaves, storms, floods and bushfires are a normal part of life in NSW. These extreme events can have devastating effects on human life and property, at great cost to the community.
The south-west of NSW, where a large proportion of our irrigated agriculture is based, is already particularly affected by reduced water availability. The many high-value assets along our coastline are susceptible to storm surges, sea level rise and increased flooding.
NSW, its people and its ecosystems will feel the effects of a changing climate in all these environments. Changes to our climate will exacerbate natural variability, making it more difficult to manage our landscapes and ecosystems and the human activities that depend on them. Communities already affected by climate variability will be challenged by a climate shift, and there will be additional demands on our emergency services and health system. Our unique ecosystems will also experience the pressure of the rapid change in climatic conditions and in their habitat.
The NSW climate
The NSW climate is highly variable over both space and time. Annual average rainfall varies from less than 200 mm in the north-west of NSW, to more than 1800 mm along the coast. Very high temperatures are regularly recorded in the arid north-west of NSW and sub-freezing temperatures are frequently observed in the southern alpine regions, although average annual temperatures across the state are generally mild.
The north-east of the state has relatively wet summers and dry winters (see figure). Conversely, agriculture in the south of the state is dependent on regular rainfall from cold fronts and cut-off lows passing through south-eastern Australia during the winter growing season. These southern districts receive little rain in summer. There is a large region of NSW where the distribution of summer and winter rainfall is fairly even (green area).
The coast of NSW is influenced by the warm waters of the Tasman Sea, which moderate temperatures and provide moisture for abundant rainfall. Moist onshore winds deposit significant precipitation on the steeply rising terrain of the Great Dividing Range. The ranges enhance rainfall near the coast and contribute to a strong east to west drop in annual rainfall across much of the state. The dry north-west of the state receives most of its highly variable rainfall in very irregular, high intensity rainfall events, which can occur at any time of the year but are more likely in summer.
Afternoon sea breezes usually moderate the summer temperatures along the coast of NSW. In contrast, the arid north-west of the state regularly experiences maximum temperatures above 35°C during the summer months. Occasionally the heat from these desert regions is drawn south and east ahead of summer cold fronts, and this produces very hot conditions in the southern and coastal districts of NSW. The very high temperatures, strong winds and low humidity ahead of these fronts increase the risk of bushfire. In winter, cold snaps may lead to inland frosts and snowfall on the alps and tablelands.
Figure. Major seasonal rainfall zones of Australia. The rainiest time of year depends on where you are. Of the six major categories that occur throughout Australia, four can be found in NSW. Source: Bureau of Meteorology. http://www.bom.gov.au/climate/environ/other/seas_group.shtml
As well as this strong spatial variability, climatic conditions can change greatly over time in many areas of NSW. The major oceanic climate drivers — the El Niño–Southern Oscillation, the Southern Annular Mode and the Indian Ocean Dipole—all interact over New South Wales producing a highly variable climate from year to year.
For more information on how the major climate drivers affect NSW, visit
Climate Kelpie.
For an excellent animation of the main drivers that influence climate in NSW, see
the Climate Dogs.
What is the difference between weather and climate?
Weather describes the atmospheric conditions over defined short periods of time such as hours or days.
Climate is the set of averages, variations and extremes of weather in a region over long periods of time. The period for estimating average climate is usually 30 years or more, long enough to sample a full range of weather.[1]
Climate is often much easier to predict than weather. For example, if you are asked on a Monday to predict whether the following Monday will be hotter or cooler, you may be able to make a prediction but with little confidence.
If you were asked ‘Will the maximum temperature on 1st June in southern NSW be colder than on 1st December?’, you would be moderately certain of the answer. Because June is in winter and December is in summer, 1st December is likely to be hotter than 1st June. However, because daily weather patterns vary, you could not be absolutely certain. For proof of this, consider Sydney’s Observatory Hill, where the hottest maximum recorded for June is 26.9°C –considerably higher than the 15.2°C lowest maximum recorded for December.
If, on the other hand, you were asked ‘Will the average monthly temperature for June next year be hotter or colder than that for the month of December?’ you would be able to answer with certainty that the average monthly temperature in December will be hotter than the average monthly temperature in June. This is because of our understanding of the seasonal climatic cycles and the weather (or meteorological) data that we have amassed over time.
Likewise, we may not be able to say exactly when extreme events (say, days over 40°C) will occur, but we may be able to say how many of these to expect over a period of years or more.
[1] Australian Academy of Science, The Science of Climate Change: Questions and Answers, Canberra, 2010
Page last updated: 22 December 2011
