The hail was very heavy, with flashing lightning in the midst of the hail
Exodus 9:24
Water and fire derive from and express the Divine attributes of mercy and severity, respectively. Thus, the uniqueness of the plague of hail was its
blend of ice and fire, Divine mercy and severity. Similarly, although this
was a particularly severe plague, as indicated by the harsh warning
preceding it, this very warning included merciful instructions how to avert it.
Only G-d can override nature and combine fire and ice. In the same way, it is only by rising above our natural limitations and connecting ourselves to G-d that we can be both strict and merciful at the same time—both for our own benefit and for the benefit of others.
—from Daily Wisdom #1