It is the horrors of hell!
St. Theresa of Avila had a vision where she saw souls falling into hell “like snowflakes.”
St. Benedict Joseph also had a vision where he relates, “I was watching souls going down into the abyss as thick and fast as snowflakes falling in the winter mist.”
In our Catholic doctrine, hell is eternal damnation. There is no more recourse for repentance. One has exhausted the limitless mercy of God. It happens when man through his earthly life has gone farthest from the will of the Father, a deliberate offense against the Holy Spirit.
Purgatory is a better place. Although it has similar conditions like hell, there is a hope for redemption after purification.
The Holy Rosary is a powerful weapon to save souls from the purgatory.