Most South Australian residents have already experienced two or three strong cold changes already this month and another one is just around the corner. Much of the state will heat up into the thirties today but only reach the mid-to-high teens tomorrow, cooling 10-15 degrees in a day. For many centres, including Adelaide, this will be the third time in the past fortnight that they have cooled more than 10 degrees in a day. For some places, including Ceduna, Whyalla and Port Augusta, it will be the fourth time in a fortnight. This will turn out to be the most changeable fortnight in six years for Ceduna, Whyalla and Port Augusta. And this comes after an up-and-down September, when a similar number of abrupt changes occurred during the month. All up this spring Ceduna, Whyalla and Port Augusta have had seven such changes. Spring is typically up and down but this one has had been more extreme than in recent years. Cold fronts had been fairly weak in winter and early spring, allowing extra heat to develop over central Australia. Now that cold fronts have become strong in the past month they are drawing hot northerly winds to the coast before bringing colder changes. The stronger fronts have also led to a windier than normal month. Knowing whether it is a t-shirt day or a jumper day has many residents listening to the forecast more closely than normal. Those carrying a jumper today will have listened to the forecast. Jumpers will come in handy later this afternoon for those in western and central parts of the state and this evening in eastern and some northern parts. Temperatures will drop by as much as 10 degrees in under an hour with a gusty wind change. Looking ahead, another change this weekend is looking more gentle, cooling most places by five-to-10 degrees. Further ahead, the following few changes will be even more gentle as heat gets shifted further north by frequent, but weaker cold fronts. Next week temperatures will be nearer average, so the jumper and t-shirt can be traded for just a long-sleeve shirt.