Yesterday was a blip in Sydney's warm start to spring, but sustained cooler weather is on its way. Sydneysiders have been spoilt for warmth in their warmest start to spring on record. Yesterday was a rare day almost right on the September average of 20 degrees. Today is quite warm in the western suburbs again as a seabreeze is keeping the city and much of the east in the low-to-mid twenties. Tomorrow will be very warm across Sydney with the mercury set to climb to around 30 degrees, from the far west to the beaches in dry and gusty westerly winds. These winds will also bring pollen and dust in abundance. It will be the hardest day this season for those with Hay Fever. A weak cool change will drop temperatures on Wednesday to the mid twenties followed by another cool change leading to even cooler days, like yesterday, on Thursday and Friday. Showers should arrive, mostly near the coast between Thursday afternoon and Friday. The drop in temperatures may come as a shock to Sydneysiders who have enjoyed the long dry and warm run. The city hasn't measured more than 1mm in a month and hasn't had a day stay below 20 degrees in 17 days. This cooling off period will help people to remember that it isn't summer yet in sunny Sydney