Caves are one of our oldest known human habitations, and there’s good reason for it. You’re out of the wind in most cases, unless the cave has its own air flow. You’re out of the rain and water is not a problem, unless the cave is prone to flooding. Caves also have stable temperatures, feeling cool in the summer and warm in the winter. In fact, when you get a few feet underground, the temperature doesn’t change much at all. The underground temperature will be affected by the area’s latitude, with caves in North America ranging between 40 to 60 degrees (being warmer in the south and cooler up north). Caves are also easier to defend than most other natural shelters (or man-made shelters, for that matter). They are not without problems, however. The three main issues with cave safety are animals, air and collapse. Bats and other animals can fill the cave with droppings (and the pathogens and parasites those transmit). You may even run into dangerous animals in the cave. Second, the air can be poor in caves, so it’s usually better to stay near the mouth of the cave (rather than the back). Finally, caves can collapse, turning your refuge into a tomb if you are in the wrong cave at the wrong time. The most dangerous caves are coastal ones (also known as sea caves). When the tide rises, these places can be blocked or even filled with water. It may not happen slowly, either. In some cases, they can flood in a matter of minutes. If you have to take shelter in sea caves, look for the high tide line and check the inside of the cave for danger. Seaweed, driftwood and standing pools of salt water are all red flags. Get out quickly, and find some other place to shelter, especially when storm surge is a possibility.