Hi Jerome,
I mentioned the temperature over the New Year because it was the highest on record for Melbourne - 41.2oC on New Years Day before a cool change thankfully dropped the temperature by 14oC. Adelaide had record temperatures as well and a lot of beer was consumed!
Don't worry, Melbourne is not always that warm in summer (average peak temperature is 26oC in December-January), so you should still visit one day.
Happy new year.
Andrew