Melburnians and Canberrans may be used to wearing black scarves, skivvies and coats at this time of year, but how long can they keep it up? They, along with Adelaideans and Sydneyites and everyone in between, may need the extra layers every day for another week, at least. Most of those who live in the south of the country are used to cold, mixed in with some relatively mild days. But this winter is a bit different. The recent cold is not a brief burst but a long-lasting one which could go well into next week, potentially the longest cold spell in three years. The last time Melbourne stayed colder than 14 degrees for more than a week was in 2007. It's also been three years since Sydney stayed colder than 17 for more than a week and Canberra colder than 12 for more than a week. For Adelaide it's been two years since there's been a seven day period in which it has failed to warm to 16 degrees. One can conclude that for much of southeastern Australia this cold spell is looking like the longest in three years. Frost will also be a feature. This morning Oakey in southern Queensland dipped to minus six degrees, their coldest in six years. Don't expect noticeable warming too soon.