The defining story of Australia's climate in 2018 was one of protracted drought and persistent warmth. 2018 is likely to be amongst the country's ten warmest years on record. Rainfall for the year (to mid-November) was exceptionally low over the southeastern quarter of the mainland, with much of the region experiencing totals in the lowest 10% of records.
Dry conditions affected much of eastern Australia over the preceding 18 months, but intensified through 2018 despite some winter rain along the eastern coastal margin.
September was an exceptionally dry month for Australia; not only the driest September in 119 years of national records, but also the second-driest for any month of the year (behind only April 1902).
This dry month contributed to a very early start to the 2018–19 bushfire season for much of eastern Australia, with serious grassfires and bushfires during August, and fire danger periods commencing weeks to months earlier than usual in New South Wales and Victoria.
Heat was less a tale of individual extremes, and more one of persistent warmth. However, there were notable events, including a January heatwave in which Penrith observed the highest temperature in the Sydney region since 1939 (47.3 °C on the 7th), record warmth in the Tasman Sea over summer, and summer-like heat across much of Australia in April.
During most of 2018, Australia's main climate drivers, the El Niño-Southern Oscillation and Indian Ocean Dipole (IOD), were neutral. During spring a positive IOD event emerged and the Pacific Ocean warmed steadily, with a late-forming El Niño a strong possibility for summer 2018–19.
The 2017–18 tropical cyclone season equalled the average number of storms for the Australian region (11), however, Marcus was the most significant in Darwin since 1974 and became the strongest in the Australian region since at least 2007.