Extreme heat waves are expected to affect an estimated 80 million people across the US this week as temperatures surge to record-breaking temperatures, and we aren't even halfway through summer yet. Wearing cooling clothing can provide relief from the heat, especially if you're outdoors or living without air conditioning. The best cooling clothes have different properties that work to keep you cooler and more comfortable. Your body temperature going down is what gives you the sensation of feeling cool. For clothing to be effectively cooling, the fabric must have properties that work together with the body to help dissipate heat and promote airflow. Ventilated, flowy and breathable clothing allows for more air to pass through, and helps prevent heat or perspiration from being trapped against the skin. Less breathable fabrics like polyester or wool, on the other hand, can keep body heat confined between your body and the material and make you feel even more sweaty. Perspiration can be annoying but it's our body's way of regulating temperature. Moisture-wicking fabrics quickly absorb your body's sweat and then help it evaporate away. The secret is in hydrophilic and hydrophobic fibers. Hydrophilic fibers absorb sweat from the skin, evenly dispersing it across the fabric. Hydrophobic fibers keep out moisture and help fabric quickly dry. Thermoregulation is how humans maintain their body temperature, and there are four different ways to transfer heat. If the fabric of your clothes is effective at any of these four methods, it can help keep you cooler. Everyone knows what it feels like to be muggy and hot in their clothes. As each summer seems to break the previous year's high-temperature record, researchers are exploring different ways to produce effective cooling clothing. Clothing and other garments can utilize non-electric cooling techniques such as ice, phase-change and radiation cooling. Early cooling clothing looked like actual ice vests that absorbed a person's body heat as ice melted, causing a physically cool feel. A lot of modern cooling clothing, like those from LifeLabs, has infrared heat-blocking abilities that offer protection from the sun's harmful rays. But experts are even working out the kinks on smart cooling clothing powered by electricity. As we continue to experience high temperatures, it's fair to expect more improvements and development to come from cooling garments. Cotton is a natural fiber that's breathable, lightweight and widely accessible. Air easily passes through cotton fabric, allowing you to feel breezy and cool. It's best for dry heat, since it's absorbent but not moisture-wicking. Bamboo is a premium natural fiber that's good at wicking away moisture. It's also even more breathable than cotton because of the "micro gaps" within bamboo fabric that promotes increased airflow. Silk is a thermoregulator that helps you keep a comfortable body temperature. It's ultra-lightweight, soft and tends to come in flowy silhouettes. Sourced from processed wood pulp, rayon is made up of thin fibers that make it feel light and breathable. It doesn't trap heat between the fabric and your body, allowing sweat to evaporate and heat to dissipate. A type of rayon, viscose is a soft and comfortable fabric that can also help keep you cool during summer. Linen is derived from the flax plant and is a well-known fabric for summer because of its lightweight and breathable feel. It has a loose weave, allowing air to easily pass through. Polyester and nylon are made from petroleum, essentially making them a type of plastic. They retain heat and even bad odor, and they don't absorb moisture. This means your sweat sits on their surface, trapped between your skin and the fabric. We all love our jeans, but they aren't the best clothes for hot weather. The material is heavy, not very breathable and can retain moisture. If you have to wear jeans, try a looser fit and a light wash to reflect the sun. Made from thick cowhide, leather is a good insulator during the winter. It also is often dyed black, a color that absorbs heat. Unless you want to be real warm, avoid leather jackets in the summer.