All correct, save a few minor inaccuracies. Estivation or hibernation is not in response to dry conditions or "high" temperatures; rather, it's an instinct meant to conserve energy in times expected to entail little food or extreme temperatures.
Besides that, all good. Your go.
According to Wikipedia, estivation is in response to hot and dry conditions (to avoid losing moisture or damage from temperatures) while hibernation occurs in warm-blooded animals when their isn't gonna be enough food.
Correct, however all of that is interrelated. For example, the lack of food in the winter is due to the colder temperatures (as it's winter) and the drought is due to higher temperatures (as it's summer.) So, it's fair to say that both
estivation and hibernation are states of prolonged torpor caused by (to some degree) extreme temperatures, and not only high temperatures, as chscioly put it.
That's how I viewed it, but I do see that most sources are saying hibernation as a response to lack of food (presumably ignoring temperature) and estivation as temp and precip. I'll put that down as something to look into later on the internet. I'm primarily referring to one source, so I might not have the most universal information right off the bat.