More information is needed though to make it more scientific. Did it freeze in the mid 1930s? His neighbours would have been able to tell him that. In what year did it stop freezing? Did it freeze every year before that point? Did it only freeze for a couple of years? Was there significantly less precipitation the years it froze thus making it more apt to freeze due to a slower flow rate?

Anecdotes usually don't have enough information to make them valuable.