Could you maybe give a more specific example of what you are interested in?
For molecular compounds, if you already have an idea how the dissociation reaction will look like, you could perform an NEB calculation of this reaction using DFT.
Then you could use the harmonic transition state theory (HTST event) analysis to obtain the reaction rate at different temperatures and from that estimate the temperature at which the reaction becomes likely to occur.
But for solids it might be more complicated. In principle running a molecular dynamics simulation while slowly increasing the temperature until you see dissociation, might give you an idea about the dissociation temperature, although very likely a bit overestimated.
However, to get the reactions right, you'd probably have to use DFT (unless you have a really good reactive potential that describes the specific reaction you are interested in), and that would severely limit the time scale of the simulation.
