aahh crazy - summer in Perth - yep it sure gets hot and can stay that way for weeks on end.
My bit of advice for you from a WA girl would be definitely try to stay out of the sun between about 10am-4pm. Dont forget we have a big hole in the ozone down in the southern hemisphere and also the highest rate of skin cancer caused by sun exposure in the world. Be smart and ride early, drink heaps of fluid and wear a good sunscreen and you should be able to ride thru those long hot summers.
The most effective way to do it, is to do it.
Amelia Earhart
2005 Trek 5000 road/Avocet 02 40W
2006 Colnago C50 road/SSM Atola
2005 SC Juliana SL mtb/WTB Laser V