Standard dough left to rise at room temperature typically takes between two and four hours, or until the dough has doubled in size. If left for 12 hours at room temperature, this rise can slightly deflate, though it will still remain leavened. Some doughs should be left to rise overnight or be kept in a refrigerator. The lower temperature of the fridge slows the yeast down, causing the dough to rise more slowly. If the dough has been forgotten in the fridge overnight, the resulting dough will be similar to a dough that had been left to proof in a warm place for the standard two to four hours.

Ingredients that do not need refrigeration are typically OK when left combined in room temperature dough overnight. But if the dough contains milk-based products, like sour cream or yogurt, they can easily go bad if left out for several hours. The U.S. Department of Agriculture advises against consuming milk products that have been left out at room temperature. If the dough was left overnight in the refrigerator set to 40 degrees Fahrenheit or below, this is not a concern.

With a refrigerated dough that has been left overnight, the flavor and texture will be similar to the original recipe. If the dough has been left on the counter, it will develop a slightly sour taste. The texture of the bread will become thicker and may not rise as much during the second rise or the final baking. If it is left overnight during the second proof, it will also be a different shape than expected, as over-proofing makes bubbles expand beyond normal and then collapse when they are baked.

Leave dough overnight, with no milk product ingredients, if you're OK with a slightly more sour, fermented flavor. Some recipes call for leaving dough out to get this flavor. Leaving dough to rise overnight also need not be an accident -- it can be done to shorten preparation time in the morning and is standard when you're making cinnamon buns.