Daily Excess Heat Factor and Heatwave Categories for historical conditions

Extreme heat is Australia’s deadliest natural hazard, claiming more lives annually than bushfires, floods, and storms combined. Effectively mitigating heat risk requires looking beyond peak temperatures to account for how the human body accumulates heat and recovers over consecutive days. The Excess Heat Factor (EHF, Nairn & Fawcett 2015) is a primary metric for this purpose, capturing both the significance of a heat event relative to local climatology and the impact of short-term acclimatization. Further refinement by linking EHF to historical mortality rates has enabled the classification of Heatwave Risk Categories (HRC, Loridan et al. 2016), which directly translate meteorological intensity into human health outcomes.

Here we present a comprehensive, high-resolution national dataset of daily EHF, EHF categories, and HRC values for the Australian continent, spanning 46 years from January 1979 to August 2025. The data are derived from the Bureau of Meteorology’s BARRA-R2 regional atmospheric reanalysis (Su et al., 2022) at approximately 11 km spatial resolution. Hourly conditions are aggregated daily, where a day is defined with 9:00 AM local-time start (approximated as GMT+9) to consider the full diurnal heat cycle together with the following night cooling period. EHF categories are calculated using a three-decade "moving" climatological reference period centred on the decade of the observation, ensuring the baseline remains relevant to the evolving climate. HRC values are calculated following established mortality-linked formulations, providing a spatially consistent view of historical health risks.

By leveraging BARRA-R2 sub-daily temperature data, this collection provides a detailed and national-scale understanding of heat hazards, bridging the gap between atmospheric modelling and public health impact. Its application spans from public health research, urban planning and infrastructure climate-risk assessments. It enables researchers to gain valuable insight and lesson-learnt from historical heat hazard exposure, and paves the way for compound hazards preparedness and adaptation.