12.4. High ambient temperatures above 77° F (25° C) causing accelerated positive grid growth or corrosion, increased self-discharge, or thermal runway in AGM (Ca/Ca) and Gel Cell (Ca/Ca) VRLA batteries. For every increase of 18° F (10° C) above 77° F (25° C), the battery's life is cut in half due to positive grid corrosion or the self-discharge rate is doubled.
If you dig around the site below, you'll find a table that says a 100% charged battery will not freeze until -77F, but a fully discharged one will freeze at +20F. When storing, cold is recommended, not heat. Kinda makes sense because most chemical reactions slow down as it gets colder. But I do agree extremes should be avoided, that makes sense too.
Several searches you can do to edumacate yourself about batteries. I usually like more than one reputable source of info......... start here.....
https://www.batteryfaq.org/
https://jgdarden.com/batteryfaq/carfaq12.htm