As confirmed by Merriam-Webster, "nonsurvivable" isn't even a word. The real words that come to mind are deadly heatwaves, lethal global overheating and fatal climate destruction.
https://www.commondreams.org/news/march-heatwave

#ClimateCrisis #ClimateDestruction #DeadlyHeatwaves

US Endured Hottest March on Record as Experts Warned of 'Nonsurvivable' Heatwaves | Common Dreams

Last month was the hottest March on record in the contiguous United States, with an average temperature of 50.85°F, 9.35°F above the 20th-century average.

Common Dreams