Which would be the hottest month in australia?

Anytime between December and March. Also depends where in Australia as climate varies greatly

January and February

January,February and march are the hottest month in Australia.

January and February are generally the hottest months, but it depends where in Australia you are. For instance, in the south of the country it gets very hot in January and February, whereas in the far north of the country (Darwin, Cairns etc) it is hot all year round.