You are right to be concerned and it's good to be a planner and thinking ahead
If you have room, someplace that is temperature controlled and where the mice can't chew through the bags (I use the spare bedroom and have two cats in the house
, you might consider buying up timothy/alfalfa cubes, timothy pellets, etc.
You could soak them and feed them, in a feed pan, in addition to your hay BUT cut your hay back a little bit, therefore stretching the hay a little further.
You'd have to sit down and do the math on how much of a trade-off the cubes or pellets are to replace a portion of the "real hay" so they still get enough forage into them.
I feed soaked timothy pellets mixed in with the supplements; none of my horses are on grain but they all get a vit/min supplement and two get things for insulin resistance.
It's going to be a really rocky ride not only for livestock owners this winter but humans as well.
Anyone can Google "United States drought map" and get their eyes opened pretty wide on any number of hits.
We're in a massive drought which, in turn means huge crop losses which, in turn means, rising prices if there's much of anything to raise the price on