Only four times in the last four decades has Adelaide shivered through three mornings below three in June. Or you could just say it's the coldest start to winter on record, in terms of nights. However the timing of these three mornings coinciding with the start of winter is more by chance than anything else. But why has it been so cold every morning? The second in a pair of cold fronts swept across South Australia on Tuesday, leaving a cold airmass in its wake. Since Wednesday, a high pressure system been producing clear skies and light winds, allowing temperatures to plummet overnight, yet producing near-average days. The last three nights have been especially cold because the high is focused just to the east of Adelaide, allowing those light winds to be coming from the land, rather than the humid ocean, where temperatures are in the mid teens. Tonight and Sunday night will both be very cold as well, with the run of nights below three potentially continuing. Those living further inland of Adelaide will again have a substantial frost risk as temperatures drop near freezing.