Summer brings longer days, higher temperatures, and for facility managers, a season of elevated risk for UPS systems. Heat is the single biggest environmental threat to uninterruptible power supplies, and most facilities don't realize there's a problem until something fails. Here's what you need to know about how summer heat affects your UPS, and what to do about it before it costs you. Heat Is the #1 Enemy of UPS Batteries Your UPS battery is a temperature-sensitive device.