It all has to do with relative humidity, which is how much water the air in a particular environment can hold. Warm air can hold more water than cool air. During the summers in Texas, the air is warm and moderately humid, especially in July and August. Crawl spaces are naturally cooler than the outside environment because they are shaded from the sun. When the muggy air enters your crawl space, it mixes with the cooler air below your home. Since cold air cannot hold as much water as warm air, condensation forms and water vapor gets trapped in your crawl space.