snowing leaves at my house

Just saw something very unusual, and was wondering if anyone can tell me what caused it.
There is no wind outside, temperature is about 25 degrees, but trees that had hardly dropped any leaves suddenly started dropping them. It was like it was "snowing leaves". In a matter of an hour or so a large maple tree went from fully leaved to almost bare.
Any ideas what would cause such a thing?
Will Renkel
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