Acorn production is set in two windows: spring pollination (oak flowers need stable warm weather to set fruit) and summer nut filling (developing acorns need water and tree resources). Both windows are vulnerable. Late freezes in April can also wipe a crop.
In predicted-poor mast years, plan ahead: prioritize food plot rotations, identify alternative food sources, and expect deer to concentrate on remaining browse and standing crops. State mast reports issue forecasts in summer and updates through the fall.