Droughts occur across a variety of time scales (weeks to decades), and may be categorised as meteorological (precipitation deficit), agricultural (plant water requirements not met), hydrological (surface water supply deficit), socioeconomic (impacting supply and demand of goods and services), or ecological (driving ecosystems beyond vulnerability thresholds). More than one type may occur concurrently at a location, and droughts may transition from one type to another as conditions evolve. 

Precipitation deficits are necessary over some period of time in order for drought to develop. However, the speed of development and the severity of the drought are influenced by factors such as high temperatures, low relative humidity, strong winds, and clear skies. Flash droughts develop very rapidly when such weather extremes persist over the same region for days or weeks. The definition of a flash drought accounts for both the rapid rate of intensification and the limitation of moisture, allowing for events where the flash drought persists and thus develops into longer-term hydrological drought.

On the seasonal scale, there are well-established links between drought in Australia and large-scale climate drivers such as the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The possible influence of such drivers on flash drought in Australia is examined here. Furthermore, given the role of high temperatures, rainfall deficits, and clear skies in the development of flash droughts, the link between heat waves and flash droughts is also investigated.