It’s not your imagination: Summers are getting hotter, lasting longer and arriving faster, according to a new study.
Researchers at the University of British Columbia found that between 1990 and 2023, the average summer grew about six days longer per decade. That’s up from roughly four days per decade found in earlier research.
Related stories
In some cities, the shift is even more dramatic. Sydney, Australia, went from about 80 summer days in 1990 to roughly 130 today — a gain of 15 days per decade, the study said. In Toronto, summers have grown by eight days per decade.
The researchers didn’t define “summer” by the calendar. Instead, they measured when temperatures climbed above what was historically typical for a given location, using climate data from 1961 to 1990 as a baseline.
“These findings challenge what we believe to be the normal cycle of the seasons,” said lead author Ted Scott, a Ph.D. student in the university’s geography department, in a news release. “When summer happens and how quickly it arrives impact patterns and behaviors in plant and animal life, and human society.”
It’s not just the length that’s changing — it’s how fast summer arrives. The study found that seasonal transitions are becoming more abrupt, with summerlike temperatures showing up suddenly instead of gradually.
That rapid shift could throw off systems that rely on seasonal timing, the researchers said. Flowers may bloom before pollinators are ready to get to work. Crops may need to be planted further in advance. Faster snowmelt in spring could increase the risk of flooding.
“An expectation in the Northern Hemisphere that June is when summer starts may be ingrained in planning and policy, meaning we could be ill-prepared for earlier heat,” Scott said.
The study also found that accumulated summer heat over land in the Northern Hemisphere has been rising more than three times faster since 1990 than it did from 1961 to 1990.
The findings are published in the journal “Environmental Research Letters.”
Get breaking news and daily headlines delivered to your email inbox by signing up here.
© 2026 WTOP. All Rights Reserved. This website is not intended for users located within the European Economic Area.
