Climate
Wilga Tree focuses on Northern Inland NSW, which for the purposes of this site comprises the North-West Slopes & Plains and Northern Tablelands forecast districts of NSW (see map below).
NSW Forecasts Districts
The climate of Northern Inland NSW varies from east to west. Rainfall averages range from more than 1000mm at the Great Dividing Range to under 500mm around Walgett. Rainfall is seasonal with predominately summer rain, although significant falls can occur in any month. There is considerable variation in rainfall from year to year. Floods and droughts are common occurrences throughout the region.
Flooding in the Northern Inland is predominantly a summer phenomena, although substantial falls have occurred at all times of the year. In the summer months rains tend to occur in short duration heavy falls associated with thunderstorms which bring rain and localised flooding over a small area, and rain depressions which can bring more than half of months total rain in only a few days, with the potential for widespread flooding.
In the Namoi Valley flood runoff is generated mainly in the hilly east of the catchment, with contributions from the Upper Namoi/Macdonald River and its subsidiaries, the Peel, Mooki and Manilla Rivers. No two floods are the same, variations in the distribution of rainfall and in the times of arrival of peaks in the sub-catchments produce considerable variability from flood to flood. In general, however, flood waters rise and fall quickly in the upper valleys, but progress relatively slowly and can persist for long periods in the lower parts of the catchments.
In the Namoi approximately 11,500 square kilometres of land are prone to flooding, the width of the inundated area in severe floods varying from 20 kilometres upstream of Narrabri to 70 kilometres near the Barwon River. Many of the towns of the region have had and continue to have flood inundation problems, the operation of Keepit, Split Rock and Chaffey Dams have modified and attenuated flows in some cases, although the primary use of these dams for water supply and irrigation limits there role for flood control. Mitigation projects such as levees at Tamworth, Wee Waa and Walgett have alleviated some of the flooding problems.
Drought is often quite difficult to quantify - the on-set of drought is difficult to define and is dependent on conditions such as existing water storage. In spite of this difficulty, periods recognised as drought affected include the 1880s, the late 1890's to 1910, the mid 1920s and 40's, 1957, 1964-67, 1980-83, and much of the early 1990s.
Thunderstorms are predominately a summer (November - March) feature of the North, although they can occur at any time of the year. In the east around 40 storms occur in the average year, while 15-20 occur per year in the west. These storms can be of high intensity and are often accompanied by hail, high winds, and localised flooding which can cause significant damage. There have been numerous reports of tornados.
There is a slight gradient in temperatures from East to West, although the most significant influence overlaying this is elevation. Temperatures in the more elevated areas of the region to the east being 4-5 degrees lower than those locations at lower elevation.
Frost are common in winter throughout the area, with snow on the higher peaks occurring every few years.
Click on the city/town name to see climate information from the Bureau of Meteorology (each link opens a new browser window).
For further information on Australia's climate see Michael Thompson's Climate and Weather Atlas of Australia and the climate pages at the Australian Bureau of Meteorology.