Regular glass can stand up to 329 F degrees in heat before the glass shatters.
Glass such as Pyrex can withstand over 400 F before it shatters because Pyrex is oven safe and can take the heat as long as it doesn't go from cold to hot really quick.
For glass to melt it takes a very high and hot temperature to see the glass melt and requires a good furnace that can get up to a high enough temperature to melt the glass.
Glass will melt at a temperature of 2,552 F degrees which is very hot and you'll require gloves to get near the glass furnace and work with the glass.
But for glass to just break it does so at lower temperatures.