# Hail stones in summer?

This has always puzzled me. Yesterday (in London) it started hailing despite it being about $20^oC$. A couple of years ago I experienced hail in Sicily when it was about $35^oC$ in the shade!. How is this possible?

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Sorry, but your Question at least does not show as much research effort as would be required to Google for hail and go to en.wikipedia.org/wiki/Hail. There are interesting details, but basically it's colder at altitude. –  Peter Morgan Jun 24 '11 at 12:07
I feel some nice answer may appear, so I'll let it stay for now -- this is way more complex than colder at altitude; in fact large temperature near the ground helps. –  mbq Jun 24 '11 at 16:46