What voltage triggers a 'low battery' signal?

I have a question on the battery (CR1632) in the Zus tire monitor system. My iphone showed two batteries were low on two sensors during cold weather (32 degrees F). I changed them. One of them I changed showed up low again. This time I checked a new battery before installation and it read 3.22 volts. Both the old batteries read 2.88 volts. What is your voltage standard for a low battery? I think the cold weather affected the reading. If I had left the old ones in the units, with warmer weather, I think they may have still been good.

Hello @Francis_Schwartz
Lower temperature does affect the battery readings, totally agree with you.
When you got the 2.88 volts, what’s the surrounding temperature?
The threshold we set to trigger the low voltage alert is 2.4 volts.