Climate conditions in Carlsbad Cavern are an exception to the average cave. With a large entrance and many miles of passages that drop over 1,000 feet (305 m), climate conditions in the cave are very complex and only remain fairly stable long distances from the entrance. The main portion of the cave is a cold trap. In winter, once the temperature outside has dropped below the temperature in the cave, cold, usually dry, air plunges into the lower part of the entrance. This cold dry air flows down the large Main Corridor and into the Big Room and Lower Cave. As this cold dry air pushes into the cave along the floor, warmer moist air is displaced, forced up to the ceiling and pushed out of the upper part of the entrance. Over a long period of time, this natural process has cooled the Big Room to an average of 56°F (13ºC), which is 12°F (-11ºC) cooler than the ends of the cave and other large cave systems in the area. This influx of cold dry air is a natural drying process that changes the relative humidity in significant parts of the cave as well. Relative humidity drops to as low as 87.5% in the Big Room during winter months and remains at about 100% during the summer months when there is less airflow exchange from the entrance.
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