Central Australia is set to bake in its hottest week since last summer as a wave of heat slowly travels east across the country. A large mass of hot air with temperatures in the low-to-mid 40s is moving from Western Australia to the east of the country, leading to a week four-to-eight degrees above average. Mid-40s heat is already being experienced in parts of WA, in York, Northam and Bencubbin, yesterday. Between now and next Monday the hottest area is likely to be Birdsville where the maximum temperature should average 43-to-44 degrees, about five degrees above the December average. The hottest area relative to average will be western New South Wales where it will heat seven-to-eight degrees above average. The area between Broken Hill, Hay, Wagga Wagga and Condobolin will reach an average of 35-to-40 degrees for the next seven days. The highest daily temperature should be 45-to-46 degrees, most likely in the north of South Australia between Friday and Sunday. This sort of heat is more typical of late summer but we have seen similar in recent early summers, even late springs. A similar wave of heat affected the region only last year, in late November-early December, and also in November 2009. During those heatwaves thousands of people suffered from heat stress. Mt Wellington in Tasmania should be the coldest place in Australia, averaging a maximum of about 15 degrees for the week, including a maximum of about nine degrees on Saturday, about 35 degrees colder than Birdsville. The colder change which is due to chill Mt Wellington on Saturday will be the change which cools most of southern and central Australia next weekend. A low pressure trough will drag moisture from the tropics with help from a cold front, bringing cloud and rain, relieving residents from the heat in the lead-up to Christmas.