What causes thermal glass panes to crack?

Used in many varieties of windows, thermal glass panes are thought to be extremely durable and efficient. Like anything else, though, they have their Achilles heel. Thermal panes are susceptible to problems, such as admitting moisture between panes and even cracking.  

While thermal panes are tempered to withstand extreme temperatures in either direction, they are weakened by too many of these extremes. Going from severe heat to brutally cold temperatures in a relatively short amount of time can eventually cause the panes to crack. 

Additionally, if the panes are larger in expanse, there can sometimes be temperature variations across the pane that weaken the glass and cause it to crack or break. The differences would have to be vast and extreme, but it's possible. There have been instances where thermal glass panes have broken during house or building fires, even when the windows are not directly exposed to the flames. This is due to the extreme heat emanating from inside the structure, making part of the pane hot while extreme cold from the outdoors cools other areas of the same glass pane.