Is it good to visit Australia at the end of May?

My family and I will visit Australia at the end of May until June. It’s my first time and I wonder if the weather will be good at this time when we get there. We’re going to Sydney for sightseeing and we’re going to swim in the Bordi beach there because we want to try it for our first time. Anyone, is there storms, snow, or any bad weather at this time? What is the average temperature in Australia in May and June? Also, were going to Gold Coast for more swimming in the beach. In fact, unfortunately our plans are fixed and we cannot changed it. Also, this is the only vacation time available for us. We have no idea what the weather in Australia is like and we only knew the weather in the US. Anyone, help inform me about the weather in Australia.