Summer heat counted: Perth, Adelaide, Melbourne, Sydney

By Julia · weather-au.com editorial team · Published 23 October 2026 · 5 min read

"Which Australian city is the hottest?" depends on what you count. Counting settles part of it. This article counts days at 35 °C or more for ten years, from 2016 to 2025, in Perth, Adelaide, Melbourne and Sydney, then looks at how those days are arranged: in long runs, or as isolated spikes. The two cases feel very different.

The figures are from ERA5, a reanalysis on a grid of roughly 25 km. A grid cell smooths the sharpest peaks and can differ from a station reading by a few degrees in either direction, so the maxima below are good for comparing cities and years, not for settling a record. For official station records and heatwave warnings, see the Bureau of Meteorology.

The scoreboard

Averaged over the ten years, Perth has 16.2 days a year at 35 °C or more, Adelaide 9.4, Melbourne 7.8, Sydney 4.7, Canberra 4.1, Brisbane 3.9 and Hobart 0.8. Perth's summer is also the driest of the four: the site's 1991–2020 normals give 41 mm of rain from December to February in Perth, against 65 mm in Adelaide, 153 mm in Melbourne and 251 mm in Sydney.

In days at 40 °C or more over the ten years, Perth counts 17, Melbourne 16, Adelaide 6, Sydney 4, Canberra 3, Hobart 2 and Brisbane 1. Melbourne is the surprise: it is a mild-looking city with 16 days at 40 °C, seven of them in the single year 2019.

The hottest day in each series: Melbourne 45.2 °C on 4 January 2019, Perth 44.3 °C on 19 February 2024, Adelaide 42.8 °C on 24 January 2019, Canberra 42.3 °C on 4 January 2020, Sydney 42.0 °C on 4 January 2020. The Hobart maximum is 40.5 °C (31 January 2020).

Year by year

Perth never has a quiet decade: its low is 4 days (2018) and its highs are 25 (2016), 23 (2022) and 26 (2025). Adelaide and Melbourne behave differently. Adelaide ranges from 2 days (2022) to 22 (2019), Melbourne from 3 (2022) to 17 (2019). Sydney has one big year (12 days in 2017), one empty year (none in 2022) and little else. Note that the hot summers do not line up across the four cities; a "bad summer" in Perth (2016, 2022) can be unremarkable in Sydney.

Spikes and plateaus

Counting days is not enough, because a run of six hot days is harder to live through than six isolated days. We counted runs of three or more consecutive days at 35 °C or more. That is a simple rule of our own, not the Bureau's heatwave definition, which compares three-day temperatures with local conditions.

• Perth: 16 runs. Perth has 162 hot days in ten years, and many of them come in blocks. The longest is six days, 18 to 23 January 2022 (39.4 °C at the peak); two others have five days, 11 to 15 December 2019 and 19 to 23 January 2025, the latter reaching 42.8 °C.
• Adelaide: 7 runs. The most severe is four days, 17 to 20 December 2019, with a maximum of 42.7 °C. Another four days come on 14 to 17 January 2019.
• Canberra: 5 runs. The longest is six days, from 27 December 2019 to 1 January 2020, topping out at 37.6 °C.
• Melbourne: 2 runs. Its 78 hot days arrive mostly alone or in pairs. The two runs are four days from 28 February to 3 March 2019 and three from 2 to 4 February 2025 (40.2 °C).
• Sydney: none. Not one run of three days in ten years. Its 47 hot days appear as 42 separate episodes, 37 of them a single day.

The data shows the pattern, not the cause. What it does say is that in Sydney 37 of the 42 hot episodes are a single day, while Perth's 91 episodes include 16 runs of three days or more.

Nights and months

Heat that lets a house cool overnight is a different thing from heat that does not. Counting nights where the minimum stays at 25 °C or above, over the full ten years: Perth 30 nights, Adelaide 22, Sydney 1, Canberra 1, Melbourne, Hobart and Brisbane none. Treat the counts as a ranking rather than a measurement: a reanalysis grid cell is not a street.

The calendar matters too, and the southern summer is the other way round from what a European reader expects. In Perth the 35 °C days fall in January (48 of the 162), February (42), December (37), March (21), November (12) and even April (2). In Adelaide January has 37 of 94, and March 8. Hot days in Sydney have a different distribution: 15 in December, 14 in January, only 7 in February.

What to do with this

1. If you travel to Perth between December and March, plan the day around the heat, not the season. Check the forecast on the Perth page and the UV map before you go out.
2. If you live in Adelaide, the number that should worry you is not the yearly mean but the run: four days in a row at 42 °C is a different event from four scattered 35 °C days.
3. In Sydney or Melbourne, a hot day rarely makes a hot spell. Runs of three days at 35 °C happen twice in ten years in Melbourne and never in Sydney.
4. Heat and fire weather overlap, but they are not the same: see fire-season weather for the combination with wind.

Period of the data cited: 2016–2025.