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The direct cause of sunstroke is exposure to extreme heat and sunlight. The first step to preventing sunstroke is to stay out of direct sunlight. This is especially true on hot days. Make sure you keep your bare skin away from direct sunlight as much as possible. If you have to be out in the sun, wear a hat or walk with a light umbrella. Trips to the beach and other outdoor locations are common in the summer. In these situations, try to give yourself a break from the sun as much as you can. Sit down under a beach umbrella or take a walk into a nearby store with air conditioning to ease some of the stress from the heat on your body. The most dangerous time of day is the time midday to the afternoon when it is the hottest. Try to go out in the early or later parts of the day if you want to enjoy the outdoors or have to work outside. Also avoid exercising outside during this time of day as well. Exercise causes your body temperature to rise, which will make the likelihood of sunstroke even worse, especially if you are in the direct sun. The sun is strongest between the hours of 9 am to 4 pm. If you can, go out in the early morning or later in the afternoon, when the sun's rays are not as intense. If you want to spend a lot of time outside in the heat, or if you have to work outside in the heat, get yourself acclimated to the weather first. Start out with small shifts in the heat, building up your resistance to the elevated temperature that you are not used to. As you get used to it, you can start spending more and more time outside, but always remember to take breaks from the heat to give your body a break.  It can take several weeks for your body to fully adjust to hot weather, so be patient and take it slow.  You can also acclimate yourself a little at a time as well. Turn off the air conditioner in your house when you know you are going outside later in the day. This will slowly raise your body temperature and help you get accustomed to the heat before you even step outside. Another way to get sunstroke is being in an enclosed space with no air flow. This can be a house without air conditioning or fans, a car without the windows open, or any other small, enclosed room that has no cool air movement. If you live in an area without air conditioning, buy fans to help circulate air. This will help cool down the temperature and lower your body temperature. You should also open the windows in the room, which will help you circulate more air as well.  Never leave yourself, a child, a loved one, or an animal in a locked car, even if you have the windows down. This can cause major problems because the air in the car will heat up to extremely hot temperatures on a warm day. The temperature in a car can go up by 20° F (6.7 °C) in just 10 minutes.  Many cities also have public cooling spaces during heat waves -- check online to see if there is one near you. If you don't have or can't afford air conditioning, try to spend time in public spaces that have it, such as shopping malls, movie theatres, museums, etc.
Stay out of direct sunlight. Avoid going out at the hottest part of the day. Get acclimated. Avoid enclosed spaces.