The trigger is not warmth, it is water hitting dry ground
The Indian Bullfrog, Hoplobatrachus tigerinus, can spend months in a state of reduced activity underground, waiting. What ends that wait is not a rise in temperature, the pre-monsoon heat in May is already extreme, but the specific sensory signal of rain soaking into soil and the drop in ground temperature that follows the first heavy shower. Research on anuran breeding phenology in South Asia identifies this compound cue, falling barometric pressure combined with substrate moisture, as the primary reproductive trigger in most Indian frog species. Warmth alone does nothing. The rains have to come.
