Cheryl Bellaire, age 13, of Lancaster, Pennsylvania, for her question:

Why does it hail only in warm weather?

It seems that a strong draft of warm, rising air is necessary to create hailstones, though naturally several other weather factors also must be present. Hail making requires a tumultuous pocket of wild winds, plus strong contrasts of moisture and temperature. The perfect place is a thunderhead, though hail often forms in a howling hurricane. The icy pellets grow in layers, as they are swished between warm and cold, damp and dry parts of the stormy cloud.

The longer they stay aloft, the more icy jackets they add and the bigger they grow. What keeps them aloft is a strong updraft, warmed by the summery ground below. They fall when they become too heavy for this rising current to hold aloft. On the continents, hail making conditions occur in summer, when there are strong contrasts between the hot ground and freezing air aloft. Over the oceans, similar contrasts may occur in winter and thundering hail storms often occur at night.