Wherever you cook or bake, results depend on many factors including food chemistry, atmospheric pressure, climate, and elevation. The higher you climb, the thinner the air and therefore, the lower the atmospheric pressure. Beginning 2,500 to 3,000 feet above sea level, altitude starts to affect all cooking, but especially baking, in three significant ways:

1. The higher the elevation, the lower the boiling point of water (212°F at sea level, 206.7°F at 3,000 feet, 203.2°F at 5,000 feet, 199°F at 7,000 feet, 194.7°F at 10,000 feet). When water boils at lower temperatures:

• It takes longer for foods to cook in or over water.

• Dense moist batter and dough take longer to completely bake in the center.

2. The higher the elevation, the faster moisture evaporates. When moisture evaporates quickly:

• The ratio of liquid to solid changes, potentially weakening the overall structure of whatever you're baking.

• Flavors tend to be less pronounced because there are fewer moisture molecules to carry aroma to the nose.

• Baked goods dry out and go stale at an accelerated rate.

3. The higher the elevation, the faster leavening gases (air, carbon dioxide, and water vapor) expand. When leavening gases expand quickly:

• Cakes may rise too far too fast—and will sink in the center or collapse when cooling.

• Stiffly beaten egg whites expand quickly until they literally pop during baking, causing a cake to collapse as it cools.

• Yeast breads can easily over-proof (rise too much).