15 September to 1 October, the weather in Sydney is usually very pleasant. September is the first month of spring, and temperatures are mild to warm during the day and cool to mild at night, although the occasional hot day and cold night will occur. Humidity is moderate, both during the morning and afternoon. Only a few fogs develop in Sydney's west and these dissipate early.
Thunderstorms are generally few, increasing in frequency only in late spring and summer.
The rainfall can vary considerably, but at 70mm, the long term September rainfall is lower than for any other month and fallls on average on only 10 days. The mean daily sunshine is 7.2 hours. On average, light to moderate SW to NW winds prevail during the morning. The afternoons are affected by the development of seabreezes. These are more evident on the coast where the afternoons have a predominance of E to NE winds.