During which phase of a thunderstorm does precipitation begin?

The correct answer is the mature phase because this is the stage in a thunderstorm's lifecycle when significant precipitation occurs. During the mature phase, the thunderstorm reaches its peak intensity, resulting in heavy rain, larger hail, and stronger winds. This phase is characterized by a well-developed updraft alongside a corresponding downdraft, which facilitates the falling of precipitation from the cloud.

In contrast, during the cumulus phase, the thunderstorm is primarily developing and building with rising air currents, but no significant precipitation has yet formed. The dissipating phase follows the mature phase, where the storm begins to weaken, and precipitation decreases significantly. The distribution phase is not a recognized phase in the lifecycle of a thunderstorm, further emphasizing that the mature phase is the one during which precipitation begins.