The belief in frogs as rain-predictors developed from accurate observation of biological and environmental patterns:

• Frogs are physiologically attuned to drops in barometric pressure and rises in humidity, which precede rain. 
• Amphibians rely on moist environments for breeding, making their reproductive behavior directly responsive to changes that indicate rain is imminent. 
• Increased frog calling before rain is due to environmental triggers that initiate mating behavior, particularly in species that breed during wet seasons. 
• Ancient Egyptian, Chinese, and Indigenous American cultures included frog behavior in their traditional weather lore. 

As with other animal-based weather signs, the belief emerged from long-term empirical observation by early agriculturalists who depended on weather for survival.