How To Avoid Getting Struck By Lightning
Thunderstorms bring lightning, a powerful force that can result in death. In July 1985, lightning at Half Dome killed two people and injured three others (two of them, critically).
Though most common June through September, thunderstorms can happen any time of the year. During July through September, the North American monsoonal weather pattern can cause moisture from the Gulf of California to flow into the Sierra Nevada, resulting in thunderstorms.
Ultimately, there is no safe shelter outside. The only safe place is in a substantial building or hard topped vehicle.
- Check the weather forecast.
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- Watch for afternoon build-up of cumulus clouds. Seek shelter or go to lower elevations if you see towering thunderheads, darkening skies, increased wind, or thunder and lightning.
Thunderstorms are most common in the afternoon. Thunderstorms often develop when the sun heats the air near the ground and pockets of warmer air start to rise in the atmosphere. Mountain ridges and peaks contribute to updrafts that fuel thunderstorms. As these pockets of air rise, cumulus clouds form. These clouds grow vertically and become towering cumulus, and may be one of the first signs of a developing thunderstorm. The final stage of development is when anvil-shaped clouds, known as cumulonimbus form. These clouds are higher and wider, and are associated with lightning.
- Even if a thunderstorm is approaching from a far away, descend as far and fast as you can before taking shelter.
Count the seconds between the flash of the lightning and the sound of the thunder; divide the number of seconds by five to get a very rough estimate of the distance (in miles) that the lightning storm is away from you.
- Consider postponing a hike in order to avoid lightning. When planning your trip to Yosemite, include time for alternative activities during severe weather. Alternative activities include scenic driving, taking a bus tour, or spending time indoors at visitor centers and museums.