There was a time when, across large swathes of the world, the seasons fed into each other in a relatively predictable cycle of warmer and colder weather. In temperate nations, frigid winter thawed into spring. Spring bloomed into summer, where extreme heat beat down until cooler weather provided autumn’s relief. No longer. A recent study of four-plus decades of global weather records found that these seasonal norms have been replaced by an expanded summertime with a dangerous surge in seasonally inappropriate extreme heat days, extending into spring and fall. “We already know that [heat] extremes are becoming more frequent. They’re becoming more intense. They’re lasting longer,” said lead author Casey Ivanovich, a climatologist at the NASA Goddard Institute for Space Studies in the U.S. “We find that over the last 45 years, both extreme dry and extreme humid heat have expanded in their seasons over about half the globe.” Phoenix, Arizona, U.S., is experiencing an earlier wet heat season and a later dry heat season, which can’t be explained by the current research. While extreme heat days are increasing in both spring and fall globally, researchers note that these shifts vary across regions. Image by Amine Abassir via Wikimedia Commons (CC BY-SA 4.0). The team, including Ivanovich, Benjamin Cook of Monash University in Melbourne, Australia, and Sonali Shukla McDermid of New York University in the U.S., isolated the hottest 5% of days occurring around the globe using data from both NASA and the European Centre for Medium-Range Weather forecasts. They…This article was originally published on Mongabay

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