Weather Facts

Water Vapor, the Natural Greenhouse Gas

Water vapor is one of the most effective greenhouse gases in our atmosphere. It is truly the most significant gas that holds the heat in. That is why those humid nights during the summer are warmer than the clear, dry nights. When the air is dry, the heat is allowed to escape into space quite rapidly. On humid nights, the water vapor in the air literally keeps the heat in only allowing small amounts to seep into space. That is why the temperature in a desert can range from over 100 degrees during the afternoon to close to freezing in the morning. The heat gained during the day just radiates back into space overnight. Most of the water vapor that is in the atmosphere occurs naturally. Only a very small amount is as a result of human activity.