Large hail (1/4 inches [6 mm] or larger) can be a sign of:

Large hail, particularly when it reaches a size of 1/4 inches (6 mm) or larger, is often associated with severe thunderstorm conditions, including tornadic activity. The formation of large hail requires strong updrafts within a storm, which are typically present in supercell storms—the types of storms that can produce tornadoes.

As hailstones are lifted by strong updrafts, they can grow larger before they eventually fall to the ground. The presence of large hail indicates a highly conducive environment for severe weather, including potential tornado formation. Thus, observing large hail can be a significant indicator for meteorologists and safety officers of the possibility of tornadic activity occurring in the area.

In contrast, other options such as aggressive lightning, extreme temperature shifts, or excessive rainfall may not have the same strong correlation with the presence of large hail, making them less relevant in this context.