Lightning has always been considered one of the biggest summer hazards of outdoor recreation, especially when it comes to peak bagging.

Are mountain tops really more dangerous than other areas when it comes to lightning, and if so, what is it about mountain tops that make them more dangerous?

First, it's important to know that lightning does have an element of randomness and no place outside is completely safe from a cloud-to-ground lightning strike.

However, mountain tops are one of the most dangerous places to be when it comes to lightning exposure. This is true for mountain tops in all ranges above and below treeline, though peaks above treeline are the most dangerous. 

This article will explain the three reasons why mountain tops are more susceptible to cloud-to-ground lightning strikes. 

1) Lightning Strikes Take The Path of Least Resistance

Updrafts and downdrafts in thunderstorms result in an ongoing collision between water droplets in the updraft and ice particles (hail or graupel) in the downdraft.

This process results in the creation of an electrical field, in which positively and negatively charged particles become separated in a storm cloud with positive charges gathering near the top of the storm cloud and negatively charged particles near the bottom.

In addition, an electrical field also develops underneath a storm with positively charged particles gathering near the surface of the earth.

These particles can gather and "accumulate" anywhere, but they are more likely to gather and rise up terrain or objects that are taller than their surroundings and closer to the base of the storm cloud. This includes tall trees, buildings, and mountaintops. 

2) Thunderstorms Are More Likely To Develop Over Mountain Ranges Than Surrounding Lowlands

Thunderstorms require three basic ingredients to form: moisture, instability, and a lifting mechanism. Orographic lift is the most common source of lift in the mountains, as warm & moist air parcels are forced to rise when encountering a mountain range, which can develop into towering cumulus clouds, and eventually, thunderstorms.

As a result of the orographic effect, thunderstorms are more likely to form over mountain ranges when all other things are equal. This is something to consider when hiking or climbing a mountain, as a storm could develop right on top of you rather than approaching from a distance.

3) Thunderstorms Develop Over Mountains Earlier In The Day Compared To Surrounding Lowlands

Orographic lift also plays a role in the timing of thunderstorms. In most instances, thunderstorms form earlier in the day compared to adjacent valleys, towns, and plains, where you may be more accustomed to mid or late-afternoon storms.

Also, solar radiation from the sun will hit mountain slopes at a more direct angle earlier in the day, heating up mountain slopes before valleys and "destabilizing" the air over a mountain range more quickly.

When significant moisture is present during mid-summer when the sun is strongest and temperatures are warmest from a climatological perspective, it's not uncommon for thunderstorms to develop by noon over higher mountain ranges – and sometimes even earlier. 

This is especially true across the Western U.S. when significant monsoon moisture is present.

10-Day and Hourly Lightning Forecasts on OpenSnow

While keeping an eye on the sky while outside is always important during thunderstorm season, you can get dialed on the timing of your hikes/climbs ahead of time by utilizing OpenSnow's hourly lightning forecast, which is available for locations anywhere in the Contiguous U.S. and across most of Canada.

This tool is useful for planning purposes so that you can safely descend from a mountain summit to less exposed terrain before thunderstorms develop. 

Learn More About Our 10-Day Weather Forecast Views

Alan Smith