For two years we have missed mulberry season. Year before last we were travelling during that one-two week timeframe they are ripe. Last year there wasn't a good crop- the trees didn't seem to be fruiting well or we just missed it, checked too late. When we first started gathering mullberries, they always seemed to be ripe the week after school got out. It's sooner, now.
So far we have only checked four trees walking distance from our house. One was still not ready- the fruits small, hard and yellow. Another was past ripe- drying out. But the largest tree had a decent fruit crop, and the smaller one closest to our house was full of nice plump ripe berries. We have a set strategy now, to get the most berries. First, pick up all the clean ones off the grass under the tree. Then spread an old sheet underneath (it still has purple stains from last time we got mulberries). Handpick from all the branches we can reach. I use a long stick to hook down taller branches into reach. Last of all we shake the branch ends and get rained on by ripe berries falling. There's tons more left way high up in the tree for the birds and squirrels.