Temp- PLEASE HELP

Daniella
Hi ladies, how do you guys ensure accurate temps? For example I live in Oz so some nights we have air con on some we don't.. Would this change my temps? How do you ensure you get the best result?
Also on a diff topic. I had 4 days of positive OPKS when did I actually ovulate? What is normally the timeframe for O when 4 days of pos?
Thanks