Sun-protection clothing is one good line of defense against the sun, but don’t forget to put sunscreen on exposed skin to help prevent sunburns. Sunscreen is absolutely essential on hikes in the sun. Always read the directions on your bottle of sunscreen, but here are the basics:
- For hikes lasting longer than 2 hours, choose sunscreen that is SPF 30 or higher.
- Apply sunscreen liberally 15 minutes before sun exposure
- Reapply after 40 or 80 minutes of swimming or sweating, immediately after towel drying or at least every 2 hours.
Learn more in our articles Sunscreen: How to Choose and Sunscreen: When and How to Use.
It’s important to drink adequate water when you’re hiking in hot weather to prevent dehydration. Dehydration can leave you feeling crummy and possibly contribute to other heat-related illnesses, such as cramps, heat exhaustion and heat stroke.
How much you need to drink while hiking depends on a number of factors, such as temperature and humidity, your intensity level, your age, your body type and sweat rate, as well as the duration of your hike. A good general recommendation is about a half liter of water per hour of moderate activity in moderate temperatures. From there, you may need to increase how much you drink as the temperature and intensity of the activity rise. For example, strenuous hiking in high heat may require that you drink one liter of water or more per hour. As you gain experience, you’ll be able to fine-tune how much you drink.
If you’re hiking with your dog, remember they need water, too. In a dry location, plan to carry enough water for your pet and bring along a small, packable bowl.
Learn more about hydration in our Hydration Basics article.
The flip side to dehydration is overhydration, or hyponatremia. This is a fairly rare condition that mainly affects endurance athletes such as marathon runners, ultrarunners and triathletes, but it’s something that hikers should be aware of.
In hyponatremia, sodium levels in the blood become so diluted that cell function becomes impaired. In very extreme cases, hyponatremia may cause coma and even death.
The symptoms of hyponatremia are similar to dehydration: fatigue, headache and nausea, causing some athletes to mistakenly drink more water and exacerbate the issue.
Preventing overhydration: The key to preventing overhydration is to monitor how much you drink.
- Don’t overdrink—Stick to drinking a few gulps of water about every 15–20 minutes and try not to drink more than you sweat. Weight gain during exercise is a telltale sign that you’re drinking too much.
- Add salt—Keep your salt levels balanced by occasionally drinking a sports drink with electrolytes instead of plain water and/or eating a salty snack, such as pretzels. You can also take salt tablets.
Heat cramps are painful muscle contractions that can happen suddenly during exercise in hot weather. It can be helpful to view heat cramps as a warning that you’re pushing your limits and that you need to slow down. It’s not known exactly what causes heat cramps, but to help avoid them, make sure you’re properly hydrated. If you get heat cramps, do some gentle stretching to try to alleviate the pain.
Heat exhaustion is your body’s inability to cope with the stress of heat. It can occur after lengthy exposure to high temperatures and is often accompanied by dehydration.
Symptoms of heat exhaustion:
- Heavy sweating
- Rapid pulse
Treatment for heat exhaustion:
It’s important to treat heat exhaustion immediately if you or another hiker is showing symptoms.
- Get out of the heat: Look for a shady spot and lay down and rest. Remove any excess clothing. If there aren’t any trees to provide shade but you have a tarp, use it to block the sun.
- Rehydrate: Drink plenty of water and if you have electrolytes or salt tablets, use some of those.
- Cool off: It can feel good to splash cool water on your face and head. If you’re hiking near a lake or stream, dunk your head or dip a bandana or hat in the water and put it on your head.
How to prevent heat exhaustion:
- Take time to acclimate: You need to ease into hiking in hot weather. It can take 10 days to two weeks to acclimatize, so be cautious and take it slow on your first few hikes of the season.
- Stay hydrated: Make sure you’re drinking enough fluids. A half-liter per hour is a good starting point, but you may need more depending on the intensity of the hike.
- Wear appropriate clothing: Choose lightweight, loose-fitting clothing that allows your body to regulate temperature and a sun hat that will shade your face and neck.
- Rest in the shade: If you need to take a break, take the time to find a shady spot rather than toughing it out under the hot sun.
- Know what you’re capable of: Be honest about your level of fitness and choose hikes that complement that.
Heat stroke occurs when your body literally overheats. It is a serious medical condition that can strike fast and requires immediate medical attention. If you see a hiking partner displaying symptoms of heat exhaustion combined with a change in mental status, he or she may have heat stroke. Pay particular attention to these signs:
- Throbbing headache
- Nausea and vomiting
- Body temperature of 104-degrees-Fahrenheit or higher (if you have a way of measuring body temperature)
Treatment for heat stroke:
- Cool down: It’s necessary to rapidly cool a person with heat stroke. Lay the hiker down in the shade, remove extra clothing and use cool water and fanning to lower their temperature. If you’re near a lake or stream, you can attempt to lay the hiker down in the water, taking care to keep their airway clear. Also, be aware that rapid cooling can cause hypothermia.
- Hydrate: If the hiker is alert enough to hold a water bottle, get them to drink water.
- Evacuate: Heat stroke can cause internal organ damage, so get the hiker out as soon as possible and head straight to the hospital for further evaluation.
How to prevent heat stroke: Follow the same tips for preventing heat exhaustion.
If you want to be better prepared to respond to medical emergencies in the outdoors, consider taking a wilderness medicine course.