The mercury tipped 28.9 degrees today in Melbourne, the hottest day since April and nine degrees above the average for October. Mildura, in the Mallee district, saw 31 degrees, seven above average, also the hottest since the same time in April. But why so hot? It all comes as northerly winds built ahead of a trough and front, dragging in interior heat. These winds meant that almost every location across Victoria made it to at least six degrees above the norm, in some cases ten. However, summer isn't here just yet. The warm northerlies of today will be displaced by a cold front from the southwest which will cause a few thunderstorms and rain during the night, dropping tomorrow's maximum in Melbourne to a mere 18 degrees. High twenties won't return until Thursday, when the cold front has passed and the warm northerlies return. Melbourne is set to reach 28 degrees by the end of next week.