Well being a native of the Pilbara for the last 5 and a bit years, it is not unusual to have the tempertures in the high 40 degrees C, even had it hit in the low and mid 50's and that's the outside temperature, so imagine how hot inside it gets inside the car.
I had a problem with my Getz, the sensor packed up and didn't work on getting to the coolest temperature. Being a Hyundai, got it replaced under warranty with no fuss.
if you are having problems cooling, that could be the problem, otherwise it could be the air conditioning needs regassing.
Our new i30 is fantastic, stock standard Pilbara special, maximum legal grade tinted windows, dash mat and air conditioning constantly on. The car is always ice cool, last trip to the next town Karratha (247km away), we actually turned the air con onto 2 to warm up (we have the SX version so manual air con)
Due to the hot heat up here, a couple of tips I learnt early on from the locals was, wind down front windows, and rear halfway, turn on aircon to recirculate, (on face) after a few minutes of travelling the hot air is cooled sufficiently to wind up the windows.