Answer: Almonds are ready to harvest when the hulls split. They won't necessarily fall from the tree when they're ready, but you can knock them from the trees. Remove the leathery hull and spread hulled nuts in the sun for a day or two.
Some almond varieties flower earlier than others and those early varieties are subject to cold weather damage which can reduce the number of nuts they produce. Your most prolific producer is probably a later flowering type.
Wish there were some hope to offer in foiling the squirrels, but they always seem to know (and raid!) when the nuts are ready.
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