My area is in Severe Drought status - our pastures were the same color as peanut butter until last week.
We've had at least five inches of much-needed rain and that started all my horses frogs and soles shedding.
The those huge bars that developed in just a few weeks (mine get trimmed every four weeks), started to soften up and break over. I had to cut them at the "bending over" point because the farrier's visit was still ten days away for two horses; I trim the other two myself.
He is probably going to shoot me for poking my hoof knife in his part of the hoof business but everything wanted to shed and I wasn't about leaving bacteria and fungus grow under those layers.
So ditto what Loosie said, except my horses are all barefoot and sole never gets trimmed unless it's showing it wants to shed and needs some help with the process