Warning dreams warn of coming danger caused by a person, the evil one or a wrong decision we are about to make. Sometimes we need saving from an enemy, and sometimes we need saving from ourselves. Warning dreams aren’t “fate,” meaning they are not definitely going to come to pass. God will often show you things in dreams so you will partner with him in prayer and change them. Sort of like those movies with alternate endings where you can use your DVD remote to decide the outcome, heeding a solid warning dream can prevent bedlam from breaking out.
"And having been warned in a dream not to go back to Herod, they returned to their country by another route." - Matthew 2:12 (NKJV)