ירמיהו, פרק ג׳, פסוק ג׳

A severe drought and the sudden halt of rainfall were meant to serve as a spiritual warning sign, urging the people toward self-reflection and repentance. The primary approach among commentators is that this lack of rain is not a random natural occurrence. Rather, it is a direct result of the people's sins and idolatry, fulfilling the ancient warning that God will shut the heavens and withhold the rain.

The specific types of vital rains that were held back are carefully detailed. The first are the strong, heavy downpours [מצודת ציון] that arrive at the beginning of the rainy season in the month of Marcheshvan [רד״ק, מלבי״ם]. The second is the late rain that falls at the end of the season in the month of Nissan, which is crucial for watering the fully grown grain and ripe crops [רש״י, מצודת ציון, מלבי״ם]. The absence of these essential rains should have naturally evoked a deep sense of shame and embarrassment among the people [מצודת דוד, ביאור שטיינזלץ].

Instead of feeling remorse, the people display complete apathy and arrogance in the face of God's punishment. To capture this brazen attitude, a harsh image is used, comparing the nation's mindset to the bare forehead of a prostitute. While modest women would hide their faces and cover their foreheads when faced with a shameful situation, a prostitute walks openly with an uncovered forehead, completely unashamed of her unfaithful actions [מצודת דוד, רד״ק]. Acting with this exact same arrogance, the people firmly refuse to feel any shame for their bad deeds or to listen to the rebukes of the prophets [רד״ק, מצודת דוד, ביאור שטיינזלץ]. In fact, the Sages teach that these two realities are deeply connected, noting that the severe drought is actually brought about as a direct consequence of the very arrogance and brazenness the people display [רד״ק].