Yes there was snow in Irvine/Tustin 60 years ago, I wasn't there, but there are several pictures to prove it.
Since at that time, this area was a remarkably agricultural area, that event should have caused some damage to the Valencias, Lemons trees.
<a href="http://web.ocpl.org/digitalmedia/v/HistoricalImages/ac2_019.JPG.html">Alice Chandler with snowman, Peters Lake (Peters Canyon Reservoir), Peters Canyon Regional Park, Orange, January 1949 </a>