dv said:

roughbarked said:

how do they define it?

In short:

Researchers from the University of British Columbia found Sydney’s summer season had increased in length by nearly 50 days since 1990.

Weather data was measured across 10 global mid-latitude cities and found the season extended for an extra 15 days every 10 years.

Sydney’s rate of warming was more than double that of most other cities analysed, including Tokyo, Paris, Reykjavík and St Petersburg.
https://www.abc.net.au/news/2026-04-14/nsw-sydney-climate-longer-summers-study/106561816