Much better than a UK summer that's for sure.
You will need jumpers as gets cold once the sun goes down and a raincoat. Around15-20 during the day and expect some rain, but there will be a lot of sunshine. I would layer stuff, don't take any thick coats as you will boil. Don't forget it can get very windy as well.
Though houses cold as no central heating, tend to be room to room heating e.g. potbelly or a gas heater type thing. Though some houses have reverse aircon/heating. Well what I have experienced when visiting rellies.
Have a look at BBC weather 5 day forecast, put it Perth and it will also show you down the bottom of the page average temp and rainfall for each month. I have it as one of my favourites, so I can torture myself every day, sad I know.
Born and bred in Perth but been in UK 19 years and trying to convince DH we need to go home, so sick of UK weather.... We can finally afford to have our dream house mortgage free but DH couldn't get a job, he is very specialised in what he does here in UK.
What joy at never having to wear a thick coat ever again... You lucky thing.🐨