On January 10, 1939 – Melbourne was 113 degrees, nine degrees warmer than this month’s hottest temperature.
11 Jan 1939 – HOTTEST DAY ON RECORD IN THREE CAPITALS Seven Deaths: Many People Collapse – Trove
Melbourne, Australia Weather Calendar | Weather Underground
This map shows all of the GHCN temperatures recorded in Australia on January 10, 1939.
It looks to me like January 10, 1939 was likely hotter in Australia than December 17, 2019.
