Darwin has just sweltered through its hottest December day in 36 years, reaching 36.3 degrees just after 2pm this afternoon. The last time it was hotter in December was in 1976, when it reached a record 37.0 degrees. It was not only Darwin which experienced rare heat, it was much of the Darwin-Daly, Roper-McArthur and Victoria River districts. Borroloola had its hottest December day in at least 19 years, hitting 43.3 degrees. The hottest in the territory was McArthur River, where it peaked at 44.1 degrees, its hottest December day in five years. The heat was brought about by southerly winds blowing off the desert, where temperatures have been reaching the forties for several days. The desert heat hasn't been so unusual but sustained southerlies are quite rare at this time of year. Southerlies are more typical between September and November, the hottest time of year for the Top End. Southerlies have been a result of a low which formed over the central Top End. The low moved a bit further west later this afternoon, causing dry southerly winds to turn more humid westerly over Darwin, which made the 'feels like' temperature reach 43 degrees. Now that the westerly wind is increasing, the city is slowly cooling, but the humidity is increasing, making it feel extremely sticky. Over the next few days Darwin and much of the Top End will gradually cool with help from a reduction of inland heat and winds in Darwin staying westerly. Unfortunately for those who struggle to cope with the sapping humidity, it will be around for a while longer.