Prolonged heatwaves are likely to be conducive to extreme tropo in
Brisbane. This is considered one pre-requisite for the potential generation of long distance tropo ducts. According to Extreme Weather:
There is no universal definition of a heatwave although it can be generally defined as a prolonged period of excessive heat, which can be anywhere from 37-42 degrees celsius. (This booklet was published in November 2010 by News Ltd in association with Nine News Qld).
Temperatures and stagnant High Pressure systems produce the most
consistent marine-based tropo ducting in Brisbane and the South East Coast. These
combined factors generally provide reception of high powered FM
broadcast stations located over 1,000 kilometres away. These
broadcasters need to be sited near the coast. See an example.