November and December vie for the title. Average maximums are extremely high, but the apparent temperature (what it feels like) is staggering due to humidity.

January is when Australia records its most extreme heatwaves. In 2019, Australia experienced its hottest month ever recorded (January 2019), with a national mean temperature of 30.0°C (86.0°F) – a full 2.9°C above average. Places like Oodnadatta, South Australia (once hitting 50.7°C / 123.3°F) see their highest temperatures in January.

Australia's heatwaves are becoming more frequent, longer, and more intense due to climate change. In January, a "heatwave" means three or more consecutive days where both daytime and nighttime temperatures are unusually high. often remain above 25°C (77°F) in cities like Sydney and Melbourne, preventing the body from recovering and increasing the risk of heat stress.