In South China, there prevails a proverb “Man can′t cook rice for the firewood is wetted by rainy weather when it encounters two solar terms of Slight Heat and Great Heat in Chinese lunar June”. The proverb is validated and its accuracy is 90%. In terms of physical meaning, it possibly reflects the effect of the annual variability of the relative phase of the moon (MPH) toward the earth on the rainfall in South China early flood season (SCEFS). From that point of view, the proverb is generalized and the correlation fields between MPH and rainfall in SCEFS and the spring persistent rain (SPR) are calculated. It shows highly significant relationships, especially MPH relates to SPR. Running correlation field between MPH and SPR shows high stability of the relationship. Their wavelet transform shows that they have same significant 2—3a periods, indicating their possible internal physical relationship. Therefore, the relationships can be applied to operational predictions as an important reference. But the mechanism is not clear. Maybe it comes from the annual variability of the tide force of moon.