On the measurement of heat waves
Open accessAbstract
Despite their adverse impacts, definitions and measurements of heat waves are ambiguous and inconsistent, generally being endemic to only the group affected, or the respective study reporting the analysis. The present study addresses this issue by employing a set of three heat wave definitions, derived from surveying heat-related indices in the climate science literature. The definitions include three or more consecutive days above one of the following: the 90th percentile for maximum temperature, the 90th percentile for minimum temperature, and positive extreme heat factor (EHF) conditions. Additionally, each index is studied using a multiaspect framework measuring heat wave number, duration, participating days, and the peak and mean magnitudes. Observed climatologies and trends computed by Sen's Kendall slope estimator are presented for the Australian continent for two time periods (1951–2008 and 1971–2008). Trends in all aspects and definitions are smaller in magnitude but more significant for 1951–2008 than for 1971–2008. Considerable similarities exist in trends of the yearly number of days participating in a heat wave and yearly heat wave frequency, suggesting that the number of available heat wave days drives the number of events. Larger trends in the hottest part of a heat wave suggest that heat wave intensity is increasing faster than the mean magnitude. Although the direct results of this study cannot be inferred for other regions, the methodology has been designed as such that it is widely applicable. Furthermore, it includes a range of definitions that may be useful for a wide range of systems impacted by heat waves.
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Heat wave definitions often lack precision and firm scientific justification.
“But, perhaps the most obvious obstacle is heat wave definitions that often lack precision and firm scientific justification. Perkins and Alexander (2013) provide a succinct assessment: 'Despite their adverse impacts, definitions and measurements of heat waves are ambiguous and inconsistent, generally being endemic to only the group affected, or the respective study reporting the analysis.'”
From Forecasting Extreme High Summer Temperatures in Paris and Cairo Using Gradient Boosting and Conformal Prediction Regions (2025) · cites this paper as Perkins and Alexander (2013)
Even when precise mathematical or statistical definitions of heat waves have been provided, key heat wave features are justified by empirical norms in climate science and meteorology or computational convenience.
“Even when efforts have been made to provide precise mathematical/statistical definitions (Perkins and Alexander, 2013; Smith et al., 2013), key heat wave features are justified by empirical norms in climate science and meteorology or computational convenience.”
From Forecasting Extreme Temperatures in Siberia Using Supervised Learning and Conformal Prediction Regions (2025) · cites this paper as Perkins and Alexander, 2013
The general definition of atmospheric heatwaves is a prolonged period where temperatures are substantially hotter than normal.
“The general definition of atmospheric heatwaves is a prolonged period where temperatures are substantially hotter than normal (Perkins and Alexander 2013).”
From A hierarchical approach to defining marine heatwaves (2016) · cites this paper as Perkins and Alexander 2013
Perkins and Alexander (2013) define an atmospheric heatwave when at least three consecutive days exceed a calendar day threshold defined as the 90th percentile value for temperature.
“Based on these criteria, Perkins and Alexander (2013) define an atmospheric 138 heatwave when at least three consecutive days exceed a calendar day threshold defined as the 139 90 th percentile value for temperature.”
From A hierarchical approach to defining marine heatwaves (2016) · cites this paper as Perkins and Alexander (2013)
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Self-citationLonger and more frequent marine heatwaves over the past century.
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“Temperature extremes are often detected as (consecutive) days exceeding a certain threshold (e.g., Perkins & Alexander, 2013; Russo et al., 2014; Sillmann et al., 2013), but approaches based on cumulative metrics, are also used (Russo & Domeisen, 2023).”
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Berk, R. A., & Braverman, A. (2025) · arXiv · doi:10.48550/arxiv.2503.16118
“Even when efforts have been made to provide precise mathematical/statistical definitions (Perkins and Alexander, 2013; Smith et al., 2013), key heat wave features are justified by empirical norms in climate science and meteorology or computational convenience.”
Berk, R. A. (2025) · arXiv · doi:10.48550/arxiv.2506.02349
“Perkins and Alexander (2013) provide a succinct assessment: “Despite their adverse impacts, definitions and measurements of heat waves are ambiguous and inconsistent, generally being endemic to only the group affected, or the respective study reporting the analysis.””
- Authors
- Perkins, S. E., & Alexander, L. V.
- Affiliations
- Centre of Excellence for Climate System Science, Climate Change Research Centre, The University of New South Wales, Sydney, Australia
- UNSW Sydney (AU)
- ORCID
- Alexander, L. V.
- Venue
- Journal of Climate
- Publisher
- American Meteorological Society
- Published
- 2013-07-01
- Volume
- 26
- Issue
- 13
- Pages
- 4500-4517
- ISSN
- 0894-8755 (ISSN-L)
- 1520-0442
- OpenAlex
- W2086825875
- Cited by
- 1,432
- References
- 1
- Citations by year
- 2026: 232 · 2025: 222 · 2024: 155 · 2023: 163 · 2022: 162 · 2021: 131 · 2020: 96 · 2019: 72 · 2018: 56 · 2017: 45 · 2016: 41 · 2015: 30 · 2014: 16 · 2013: 9
- FWCI
- 14.63
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Climate (publishedVersion)
- UNSWorks (University of New South Wales, Sydney, Australia) (submittedVersion, cc-by-nc-nd)
- UNSWorks (UNSW Sydney) (submittedVersion, cc-by-nc-nd)
- ANU Open Research (Australian National University) (submittedVersion)
- Funders
- Commonwealth Scientific and Industrial Research Organisation
- Topics
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
- Physical Sciences › Environmental Science › Global and Planetary Change › Hydrology and Drought Analysis
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Climate Change and Health Impacts
- Keywords
- heat waves, heat wave definition, heatwave frequency, heatwave intensity, temperature percentiles, Australian climate, climate change
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