Temperature for starter

Hi

I live in South Australia and bake bread most weeks.  I have been reading many posts on sourdough, and have quite a few books too.  Although I don't really like sourdough bread I am thinking about attempting a starter (hey, I didn't like white bread till I made my own!).

My question is, temperature.  Here in this great southern land, the temp can be 40degC for a day or three and then be 23degC the next.  Leaving the starter to ferment out on the counter for many days, doesn't sound like a good idea if the temp soars.