A campfire that looks like it's out might not be out and could easily reignite with enough air, oxygen or wind. So when you're putting your campfire out at the end of the night, you want to make sure it's completely, for sure, 100 percent out. And the way to do that is with water.
So first you want to make sure that the fire has burned down to white ash. And you can stir it around a little bit and you'll see that everything that was black is now white. And then grab some water and pour the water over the fire and stir again. And you want to get to the point where you're not seeing anymore embers. You feel really confident that it's completely out.
Sometimes a fire can just reignite with a little bit of oxygen or even the warmth of the sun can get it going again. So a fire while you're sleeping in windy conditions could lead to disaster. So just make sure that when you're going to bed at night your fire is out and you use water to get it completely out.