HEAT AND COLD

Australia is not only a dry country, but is also subject to fierce heat. By November, average maximum temperatures over northern and central Australia have already climbed to the high 30s - and into the low 40s in parts. The heat does not relent until the following autumn.

Heat waves
On occasions, the hot air extends south over the southern States. Occasionally, these "hot weather" patterns become slow-moving, and the cold front bringing a cool change stalls, or even dissipates. On such occasions, very high temperatures - high 30s or even 40s - can persist for days, and in inland areas, for weeks on end. These are the "heatwaves" of the southern States. Such heatwaves can lead to heat exhaustion, and even death, particularly among the very young or old. Heatwaves have, in fact, accounted for more deaths in Australia than any other natural hazard. According to Energy Management Australia, the January 1939 heatwave in South Australia, Victoria and NSW killed 438 people.

“A typical hot weather situation over southeastern Australia, with hot, dry northerly winds ahead of a cold front. This situation, on 16 February 1983 - the day of the Ash Wednesday bushfires in Victoria and South Australia - produced temperatures up to 45ºC.”

Cold and snow
On the other hand, Australia is largely spared the extremes of cold that afflict many northern hemispherecountries. Outside the highland areas of southeastern Australia, snow is something of a noteworthy event. Occasionally, however, snow will fall to near sea-level, or a northward-moving pool will bring snow along the Great Divide as far north as southern Queensland. A typical weather situation producing low level snow is when south to southwesterly winds rapidly transport very cold air northward from far southern latitudes.

Low overnight temperatures in Canberra during July 1994, combined with a malfunctioning automatic sprinkler, produced this display of icicles on play equipment at a Canberra pre-school centre (courtesy of Gary Schafer, Canberra Times).

At the higher elevations of southeastern Australia snow often persists for weeks or months at a time. However the amount of snow that falls can vary substantially from year to year. In some years, such as 1973 (when it was too warm) and 1982 (too little precipitation), the ski season fails. On the other hand, some years (such as 1981) have abundant snow and a "bumper" ski season. In recent years, snow-making equipment has reduced somewhat this uncertainty for the ski industry.

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