Sydney suburbs are often distinguished by property prices but last night it was rainfall and some of the more affluent areas copped a mighty downpour. Heavy falls flooded the lower north shore, CBD and eastern suburbs yet just a few suburbs away there was just enough rain to water the garden. Several suburbs further west it was not even enough to wash the car. In the lower north shore, CBD and eastern suburbs as much as 80-to-100 millimetres of rain came down in a hurry in the few hours around midnight including more than 50mm in under an hour. This was the biggest downpour in 12 months and led to properties being inundated and roads going under water. Only about five kilometres away from the flooded suburbs, Chatswood picked up 19mm, its heaviest rain in just a week. About eight kilometres from Little Bay which was drenched by 81mm, is a significantly drier Sydney Airport which only gained 17mm. West from about Holsworthy, Liverpool and Seven Hills, rain was much lighter, bringing as little as about two millimetres or less. What brought the rain? Humid northeasterly winds converged with cooler southeasterlies which were sent in by a front moving up the coast. Why was the rain so heavy? The front slowed down to near-stationary for a few hours, keeping the same group of suburbs under the influence of the converging onshore winds. Why was the rain focussed so much over eastern parts of the city? The front was just too weak to take the southeasterly winds and the heavy rain a long way inland. What's to come? The front has now moved off the coast, taking the highest instability and heaviest rain with it. Wind is turning northeasterly throughout and is becoming more stable. For the rest of today, a few heavy showers are still possible near the beaches while the odd shower affects some inland suburbs. On Tuesday and Wednesday the air will warm up and skies clear as wind turns more northwesterly ahead of another front. Wednesday will warm to the thirties away from the coast. Some western suburbs should reach the mid thirties, potentially their warmest April day in 10-to-20 years. The front will bring a cooler change that night, making Thursday as much as 10 degrees cooler than Wednesday.