What’s a Heat Dome?

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Following a North American hot weather event in June 2021 (Henderson et al., 2022; Jain et al., 2024; Wettstein et al., 2024), the term “heat dome” was officially recognised by the American Meteorological Society in 2022. They define it as “an exceptionally hot air mass that develops when high pressure aloft prevents warm air below from rising, thus trapping the warm air as if it were in a dome.” Heat domes have also been likened to the trapping of heat in a similar manner to a lid on a saucepan. The heat dome is visually summarised by Figure 1.

Figure 1. How heat domes occur (Credit - Washington Post)

Headline text reads: "What is a 'heat dome' and why is it super-heating Australia?"

Figure 2. An example heat dome headline (Credit - Weatherzone)

The term "heat dome” has not been commonly used in Australia, despite the impact of the 2021 North American event. For example, it was the deadliest weather event in Canada’s history, with 619 heat-related deaths during the 7-day heat dome in British Columbia. But the record-breaking heatwave of late January 2026 (Figure 2), that was due to a heat dome, exposed a large population to severe heat and saw usage of the term increase (Figure 3). With projections for more frequent and severe heatwaves, heat domes are likely to become more familiar.

Figure 3. January 24-28, 2026 heatwave maps and January 26, 2026 forecast temperatures (Credit - Bureau of Meteorology; Australian Broadcasting Corporation)

References

Henderson SB, McLean KE, Lee MJ, Kosatsky T. Analysis of community deaths during the catastrophic 2021 heat dome: early evidence to inform the public health response during subsequent events in greater Vancouver, Canada. Environmental Epidemiology. 2022;6(1):e189.

Jain P, Sharma, AR, Acuna DC. et al. Record-breaking fire weather in North America in 2021 was initiated by the Pacific northwest heat dome. Commun Earth Environ. 2024;5,202.

Wettstein ZS, Hall J, Buck C, Mitchell SH, Hess JJ. Impacts of the 2021 heat dome on emergency department visits, hospitalizations, and health system operations in three hospitals in Seattle, Washington. JACEP Open. 2024;5(1):e13098.