At this time of year Sydney would typically receive about 100 millimetres of rain during a three week period but the city has not had any rain for more than three weeks and is close to breaking a dry spell record. This is Sydney's 23rd consecutive dry day - for the first half of winter there have only been four longer dry spells in 156 years of records. The record dry spell for this time of year is 25 consecutive dry days, set in both 2002 and 1962. With no measurable rain likely until at least Sunday, Sydney is on target to break the record. What makes this year different to previous years is the lack of moisture in the atmosphere and the strength of cold fronts. Moisture is sourced when winds blow off from the oceans, but during the past few weeks winds have generally been from the west, off the land. This is largely a result of stronger-than-normal cold fronts crossing southeastern Australia. These fronts have delivered a fair amount of rain to parts of western New South Wales, Victoria, Tasmania and South Australia and plenty of snow to alpine areas. With another strong cold front or two to come, winds should continue to blow from the west and carry very little moisture east of the Great Dividing Range. Sydneysiders will have to endure a few more cold nights but get to enjoy sunny days. The next best chance for winds to turn onshore is this Sunday when southerlies look like developing in the wake of a front to bring a few showers. If no rain is recorded by Saturday, Sydney will have broken a long dry-spell record for the first half of winter. The lack of rain together with strong, drying winds has led to falling dam levels. Warragamba dam is at 84% capacity, its lowest level in two and a half years. Rainfall and dam level deficiencies are at critically low levels in the far west, far north and along much of the NSW coast, including the Menindee, Tibooburra, Casino and Kempsey areas. From early next week some moisture should flow in from the tropics and help bring some more significant rain to northern and eastern NSW.