Temperatures stayed above freezing point overnight, but icy winds meant it felt as cold as minus three in some parts of the Illawarra this morning.According to Bureau of Meteorology weather monitoring stations, it felt like minus three degrees at Albion Park at 8.15am today, while at Bellambi it felt like minus 1.5 at 8.30am.The Bureau predicted severe frosts in the hinterland and winds of up to 45km/h across the Illawarra, leaving no doubt that winter has arrived.Daytime temperatures in Wollongong will struggle to push past 15 degrees today and tomorrow, although the bitterly cold winds will make it feel two to three degrees colder.A relatively balmy top of 17 degrees is forecast for Friday.Meteorologists say the collision of a low-pressure system east of Tasmania and a high pressure system south of Western Australia is dragging frigid air from the Antarctic north over south-eastern Australia.Temperatures below freezing are not unheard of in the Illawarra, although they are rare, with just a handful recorded in recent decades.According to a monitoring station at Albion Park, residents shivered through temperatures of minus two in June 2006 and again in August 2009.The mercury has never dropped below zero at the University of Wollongong weather station, which recorded climate data for 38 years before it was closed in 2008.The cold air is welcome news for NSW ski resorts, which are due to open on Friday with the Snowy Mountains of Music Festival.Perisher Blue spokesman Neil Thew said the resort started 100 snow guns on Sunday night that would run through the week to supplement expected snowfalls.