Severe Thunderstorms and Hail in Victoria
Temperatures near the tops of thunderstorm clouds are very cold, dropping to around -50 to -60 degrees Celsius even during the summer months. Hailstones form in this very cold environment when super-cooled water droplets freeze onto ice crystals, then grow in size as they are held aloft by powerful updrafts of air within the storm. The hail falls to the ground when it moves outside the storm's updraft, or grows to a size that cannot be supported by the storm's updraft.
Large hail (defined as 2cm or more in diameter) in Victoria averages about 20 reports each year. Large hail can occur in any month, but is particularly common from October to March, and reaches maximum frequency in January. During winter months hail is commonly small in size (less than 2cm).
The most damaging hailstorm to date in Australian history occurred in Sydney, NSW on the evening of 14 April 1999. This violent storm produced hailstones with measured diameters at 9cm, although larger hail would certainly have fallen in the more severely-damaged areas.
Recent examples of hailstorms in Victoria include: