Sydney sweltered through its warmest night since last summer, when the record breaking minimum of 27.6 degrees occurred. At midnight it was still 28 degrees and the official minimum was a steamy 25.3 at sunrise, 6 above average. The heat was accompanied by high humidity, staying above 70% all night long. This produced very uncomfortable sleeping conditions, and may explain any worse-than-usual midweek fatigue. It was a similar story in nearby Newcastle where it remained near 26 degrees overnight. In fact, it was cooler during Monday afternoon than it was after sunset. This was due to the winds shifting from easterly to northerly, drawing in warmer air. At Williamtown the minimum was 24 degrees, 6 above average and the warmest January night in 21 years. The hot and humid night can be blamed on the approach of a low pressure trough, which drew in warm, moist air from the north during Monday. This created high humidity and cloud cover overnight, the perfect recipe for uncomfortably warm summer nights. Luckily, relief is here in form of a southerly wind change. Temperatures are already dropping back in Sydney following this change and the cooling trend will be reinforced by a second stronger change this evening. Sydneysiders can expect a far more pleasant overnight low of 19 degrees, which is on right on average for this time of year.