You should also avoid leaning against concrete walls or lying on concrete floors during a thunderstorm. Concrete may contain reinforcing steel or other metal components that can conduct electricity. Although injuries through concrete structures are less common than some other lightning-related injuries, avoiding direct contact is a sensible precaution. <Cite refs={["turn774753search0","turn774753search6"]}/>
5. Why Standing Under a Tree Is Not Safe
Trees are common places for people to seek shelter when rain begins suddenly. Unfortunately, an isolated tree is one of the places you should avoid during a thunderstorm.
A tree can be struck directly by lightning. Electrical current may then travel down its trunk, spread through nearby branches, or pass into the ground. Someone standing close to the tree may be injured even if lightning never directly touches their body.
A side flash can occur when some of the current jumps from a struck object to a nearby person. Ground current can also spread outward from the point where lightning enters the earth.
For this reason, sheltering beneath a tree is not a reliable strategy. The same applies to standing near utility poles, fences, tall isolated structures, and exposed metal equipment.
If you are hiking or working outdoors, monitor weather conditions early and leave exposed areas before the storm reaches you. If you hear thunder, do not wait for heavy rain to begin before seeking shelter.
A substantial enclosed building is preferable. If one is unavailable, a fully enclosed hard-topped vehicle with its windows closed is generally a safer alternative than remaining outdoors. <Cite refs={["turn774753search1","turn774753search3"]}/>
6. How Far Away Is Lightning? Understanding the Five-Second Rule
6. How Far Away Is Lightning? Understanding the Five-Second Rule
The time between a lightning flash and the sound of thunder can help estimate how far away the lightning occurred.
Light reaches your eyes almost instantly over ordinary storm distances, while sound travels much more slowly. At typical atmospheric conditions, sound travels approximately one kilometer in three seconds.
To estimate the distance in kilometers:
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Observe a lightning flash.
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Count the seconds until you hear the corresponding thunder.
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Divide the number of seconds by approximately three.
For example, if 9 seconds pass between the flash and the thunder, the lightning occurred roughly 3 kilometers away.
In miles, dividing the number of seconds by five gives a useful approximation. A 10-second interval corresponds to roughly 2 miles.
However, this calculation has an important limitation: it estimates the distance to a lightning discharge, not whether your location is safe.
Lightning can strike away from the heaviest rain and beyond the area that looks most threatening. A long interval between a flash and thunder does not mean you should remain outdoors.
If you hear thunder, seek shelter immediately. You should not use the calculation to decide whether it is safe to continue gardening, swimming, exercising, or working outside. <Cite refs={["turn774753search4","turn774753search9"]}/>
7. Why You Must Wait After the Storm Seems to Have Passed
One common mistake is returning outdoors as soon as the rain stops.
Thunderstorms can produce lightning before the rain begins, during heavy rainfall, and after the main storm appears to have moved away. A brief period of sunshine or a patch of blue sky does not necessarily mean the lightning threat has ended.
Lightning can also strike well away from the main area of precipitation. This is why weather safety guidance recommends remaining in a safe shelter for at least 30 minutes after the last sound of thunder.
During this waiting period, avoid outdoor activities such as gardening, washing vehicles, playing sports, swimming, or working in an open yard.
If thunder begins again, restart the waiting period after the last thunderclap.
For people who work outdoors, this rule is particularly important. Construction workers, farmers, maintenance staff, and people who work on roofs or near power lines may have limited opportunities to reach shelter quickly. Planning ahead is much safer than waiting until the storm is overhead. <Cite refs={["turn774753search5","turn774753search10"]}/>
8. What Should You Do If You Are Caught Outside?
If you are outside when a thunderstorm approaches, your priority should be to reach a safe shelter as quickly as possible.
A substantial building is the preferred option. A fully enclosed vehicle with a rigid metal roof and its windows closed is another reasonable option when a suitable building is unavailable.