Veteran survivalists innately understand the Rule of Threes. The Rule of Threes is as follows: humans will die after 3 minutes with no air, 3 days without water, or 3 weeks of going without food. At least, those are the most commonly known rules. One that is equally essential and that gets glossed over is the fact that people can die in three hours without shelter that thoroughly protects them of fatalities in harsh conditions.
You may not think the weather in your area is harsh enough to kill you but you might be surprised. During a 1964 race in England, three competitors were cut down by the cold even though it never dropped to freezing temperatures. Even without the threat of imminent death, you can still face abundant health risks if you spend an extended period of time exposed to the elements. You name it, Heat, UV rays, cold, rain, snow, all these and more can quickly shorten your lifespan if you are continually exposed to them without a proper shelter to safeguard yourself.