How warm must dough be in order to rise?
Optimal yeast growth happens at around 37 degrees Celsius (98.6 degrees Fahrenheit), but dough will rise at any room temperature. As the temp rises, the yeast becomes more active, which is why you'll sometimes see recipes call over overnight rests in the fridge, where activity slows or stops. Yeast dies at anything above 50 C (122 F).

The important thing is knowing the temperature and, if you're really particular, the humidity in the air around your proof. This information is used for the sake of timing consistency, more than anything else.