Interesting used to live in Oz, it was hot at times. But I'd rather be hot than have a serious head injury
Not wearing a helmet is no different to not wearing a seat belt in a car, it a basic safety precaution. On or off road its common sense..
Take little pleasure from cycling on the road, about 2 in 10 don't give enough room.
On another point, amazes me around half cyclists don't wear a helmet, should be made law