How to Mitigate Thunderstorm Risk in the Backcountry
A great example of where not to be camped during a storm.
Thunderstorms can be one of the most terrifying hazards that come with spending time in the mountains. This past weekend the Somewhere Outside team was caught in a scary thunderstorm situation. We were camped in a very exposed area and an unexpected storm rolled in after we had tucked away into our tents for the night. It was the single scariest storm threat we have ever experienced - thunder bellowed and lightning flashed simultaneously while multiple inches of hail fell to the ground. We are writing this blog to ensure you have the awareness and knowledge to make decisions to avoid a similarly frightening situation or reduce the chance of harm in a worst case scenario. Please note these are our well researched suggestions - we are not meteorologists!
Each mountainous region has it’s own weather pattern but thunderstorms occur in every range across North America. The most active area for thunderstorms is the central Rocky Mountains in Colorado and New Mexico. These areas are a hotbed for thunderstorms and lightning risk, especially considering how much terrain sits exposed above tree-line. Storms are frequent throughout the rest of the Rockies but less so than these two states. The Sierra Nevada typically experiences long dry periods but thunderstorms can occur along the crest, especially if monsoons move west. The mountains along the West Coast receive fewer thunderstorms due to the cool waters of the Pacific Ocean, particularly the Cascades in Oregon and Washington and the Coast Mountains in British Columbia. The Southern Appalachians receive the most thunderstorms in the Appalachian range.
Severe thunderstorms pose many threats including flash flooding, tornadoes, wind gusts, hail and lightning. While floods, tornadoes, wind and hail can cause immense danger and damage in the mountains, lightning is the most commonly dangerous threat as it is present during every storm. Thunder booms as a result of lightning - lightning generates rapid and extreme heat (50,000°F) and expansion of the air which causes shockwaves that make the sound known as thunder. This means anytime thunder can be heard lightning is already occurring and you are in danger. Lightning is unpredictable, it often strikes without warning and can strike as far as 10 miles (16 kilometers) away from the center of the storm. The closer thunder sounds, the closer lightning is striking - if thunder and lightning are occurring simultaneously the storm is directly above you and lightning is striking in your immediate vicinity. If you see lightning and cannot hear thunder (often called ‘heat lightning’), the thunderstorm is too far away for the thunder to be audible.
There are many ways lightning can strike victims. A direct lightning strike has the most deadly outcomes but is relatively uncommon unless you are out in the open. The two most common ways to be struck by lightning are indirect strikes through ground current or a side flash. Ground current occurs each time lightning strikes an object - the electrical current travels away from the strike along the ground and spreads out radially outward and downward. The magnitude decreases with distance but the travel distance depends on the resistivity of the ground. To avoid ground current, stay away from objects that attract lightning (tall trees, bodies of water, metal). Side flashes occur when an object is hit and the current is traveling toward the ground but arcs or jumps horizontally to a nearby object to take the path of least resistance toward the ground. This typically happens when a victim is within a few feet of the object that is struck (ex. taking shelter under a tree avoiding hail or rain).
Know Before You Go
Prevention is the best way to avoid a lightning incident. Evaluate thunderstorm risk before heading into the backcountry no matter the terrain, distance, intensity or type of adventure. The most reliable storm forecasting is through the National Weather Service (NWS). To determine the storm and lightning risk for your adventure, type in the closest town or landmark (many well-known peaks and lakes are included) and use the map to zone in on the exact terrain and elevation you will be visiting. Read the written forecast and click on the hourly forecast to determine the exact timing of impending storms (or other elements of interest - cloud coverage, wind, etc). The NWS forecasts all weather elements as far out as 7 days. The NWS will also post WATCH and WARNING messages if they expect severe weather patterns in the area. Another helpful resource is the Open Summit app as it is super easy to use and accessible on a smartphone. Similar to NWS, Open Summit shows forecasts for the following 5 days and has precise forecasting for well known peaks and lakes. If you will be on a trip for longer than the weather is forecasted (5-7 days), use a satellite communicator to communicate with a friend or family member at home who can provide an updated forecast for the days unknown.
Once you have gathered storm information, you can assess the risk of a day hike or trip and make a better informed decision on whether or not to go, what time to set off, what time to be back to your car if day hiking, where is appropriate to travel and at what time of the day and alternatives if weather rolls in faster than expected. For example, you might decide to alter your route to stay below tree-line or stay off peaks, summits and ridges or you might plan a multi-day trek with low mileage to ensure you are away from exposed sections of trail before predicted storms roll in, typically in the afternoons.
While making a day or trip plan, always note the safest places to be or camp in the case of a storm. It is important to know where you could bail to in a worst case scenario. The safest places during a thunderstorm are below tree-line, in a valley or depression, away from the tall or lonely objects (i.e. a lone tree or a small cluster of trees) which might be targeted and away from exposed areas where you could be at risk of a direct strike.
If you’re heading out in a group, make sure everyone in the group is thunderstorm educated and make a plan for how to deal with a severe weather emergency.
On Trail
While on trail, get into the habit of visually monitoring the skies at all times and pay close attention to any warning signs. Don’t let a dry forecast fool you - a storm can move in unexpected. Darkening skies with tall or towering clouds and increasing wind are giveaways of an approaching storm. If you identify a storm moving in, even if lightning or thunder are not apparent, head to safer ground . The first lightning strike of a storm can happen in your location before you have seen or heard evidence of lightning or thunder. It can be really difficult to make the decision to turn around on a day hike or to retreat on a section of trail you have already completed on a backpacking trip but it could save your life - don’t think twice. Always keep an eye out for places that might be safe during a storm that you might not have noted while researching the area.
When a storm is looming -
If you can get to a building with plumbing or electricity or a metal-topped car, that is the safest place to be.
Head to lower ground to avoid elevated, exposed and wide open areas (immediately descend from any summits, ridges, saddles or anywhere above tree-line).
Avoid being near water, caves or metallic items (gear, fences, poles and power lines).
Avoid solitary trees or tall objects.
Locate yourself to the closest low lying area, below tree-line in a uniform clump of trees.
Bundle up in your insulating layers and rain gear - thunderstorms bring extreme cold with wind and hail.
When A Storm Hits
Always choose a lightning safe campsite to ensure you are prepared for a possible storm. Your tent itself cannot protect you from lightning and metal or aluminum tent poles will attract lightning. Choose a campsite that is below tree-line at a lower elevation and avoid camping under a tall, lonesome object or small cluster of tall objects such as trees to avoid ground current, side flash or the tree igniting or falling down. If you are camping below tree-line in a wooded area, find a spot protected by a low clump of uniform trees. Stay away from the tallest trees in the woods if they are not uniform. Avoid any areas that might flood if enough rain falls. If you are camped in a low risk area and do not have metal tent poles, you are equally as safe inside your tent as outside so you can stay inside to remain dry and warm.
If you hear a storm rolling in and are camped in an exposed area, relocate your tent to a lightning-safe location if you have the time and can do so safely. Try to locate a nearby depression or the lowest point in the area, preferably densely forested where you can tuck into some low trees or brush. If it is not realistic to relocate your camp, leave your tent in your weather-proof gear and relocate yourself. It sounds counterintuitive as you feel safer in your tent but a tent offers no protection in an unsafe location and can be the most attractive thing for lightning to strike, especially if you are the highest object in the area. Hike to a safer location and wait out the storm there.
No matter your location during a storm, it is a good idea to insulate yourself from the ground. Get on a sleeping pad or other insulating material to separate yourself from the ground. Drop into a lightning crouch to make yourself small and have as little contact with the ground as possible. Crouch into a ball with your heels held tightly together on the balls of your feet. It is crucial to have your feet together to have one point of entry for voltage to minimize current if struck. If voltage enters your body at multiple anchor points (i.e. separated feet), it will enter at different voltages which will drive current through your body. Do not lie down or lay in fetal position. The lightning position will not avoid being struck but can limit the severeness of injury if you are struck. If you are with a group of people, space out tents or stand ~50 ft apart in the lightning position to avoid multiple injuries from the same strike.
Many people are hit by lightning because they resume recreating too soon after they believe a thunderstorm has ended. Continue to watch the skies to determine which way storms are moving and wait a minimum of 30 minutes from the last thunder clap to resume activity, abandon the lightning crouch or return to your tent. It is not uncommon for multiple thunderstorms to roll through one after another in summer months.
This blog is not meant to scare you but to help you understand the hazards and risks associated with lightning to avoid panic in a storm situation. If you prepare and take appropriate actions, you can significantly reduce the chance of harm while recreating outside. Stay safe out there, campers!