The summer months bring the highest temperatures, great for enjoying the beautiful beaches, but January to March can be humid and also bring rainfall. The wettest month is generally in June, but winter is otherwise known for its cold drier weather patterns. Spring brings with it, fine mild days perfect for hiking and still cool enough to enjoy a red wine by the fire at night.
You can learn more about the weather to expect in Sydney and the Blue Mountains below, along with the Central Coast, Byron Bay and Lord Howe Island (which is a two-hour flight east of Sydney).