Why Does My Piano Go Out of Tune When It Rains?

Notice your piano sounding sharp during a heavy rainstorm? Learn how sudden humidity spikes affect the spruce soundboard and string tension.

Many pianists are perplexed when their perfectly tuned piano suddenly sounds harsh or sharp immediately after a heavy rainstorm. The reason lies in the hydroscopic nature of the piano's spruce soundboard. Wood absorbs and releases moisture constantly. When a storm rolls through Toronto, the indoor relative humidity can spike rapidly. The soundboard acts like a giant sponge, absorbing the moisture and expanding. Because the strings bear down on the bridge (which is glued to the soundboard), this upward expansion pulls the strings tighter, raising their pitch. Once the weather dries out, the wood shrinks, and the pitch drops back down. This constant micro-stretching weakens tuning stability over time, which is why we highly recommend installing a Dampp-Chaser humidity control system.

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