you can start whenever you want. Some people don't temp during Af, ad others do. I found that when I didn't, it was hard to get back intot e routine of temping once AF was over. But, start tomorrow, and you'll be off to a good routine! ;-)
Just a note, adding to what the PP said - though it's not stricktly necessary to temp during AF, DO IT ANYWAY. Like anything else, it's easier to remember if you do it every single day, instead of 3 out of four weeks.
Same reason they put the placebo week in packs of BCP.
I like to post everyday!!!!!!!!!!!!!! I think its fun to know how my body is every day of my cycle and it gets addicting i find myself getting excited to go to bed just so I can see what my temp will be in the morning.