Melbourne has been treated to t-shirt weather over the last few days, however a cold and gusty change will ensure a cold end to the week. Thanks to a warm air mass and large high pressure system, maximum temperatures have been sitting a couple of degrees above the September average of 17 since Sunday in Melbourne. It was warm again this morning as northwesterly winds strengthened ahead of an approaching cold front, drawing down heat from the nation's interior. The mercury reached 20 degrees around 1:00pm, three above the normal spring maximum. This afternoon cloud will build over the city, causing temperatures to gradually decline. A southwesterly wind change and the onset of rain tonight will then bring the day to a rather bleak close. This evening Melbourne residents can expect around 10-20 mm of rain. Temperatures will drop to below 15 degrees in the early evening and fresh southwesterly winds will also bring a wind chill, so residents should equip themselves with coats and umbrellas for their evening journeys home. Cloud, showers and brisk southwesterly winds will hang around on Thursday and Friday, and the mercury will struggle to reach the mid teens. Fortunately, a building high will bring warmer days with light winds over the weekend. This will allow temperatures to warm back up to near 20, permitting locals to crack out the t-shirts once again.