long continued rains
霃 centers on prolonged, unbroken rain: a long spell of wet weather that continues without clearing.
霃 combines 雨 (rain) with 沈 (sink, submerge), suggesting rain that sinks in or persists. The exact historical development is uncertain, but the component relationship is clear.
Rain 雨 pours down and sinks 沈 into the ground, day after day without stopping. Picture a field so waterlogged that the rain just keeps soaking in—long continued rains.
For チン, imagine the sound of endless rain on a tin roof: tin -> チン, and the rain just keeps drumming on and on.