EMC Question of the Day: April 1, 2023


During a thunderstorm, the safest place for a cow to be is  

  1. under a tree
  2. in a wooden barn
  3. in a car
  4. on a golf course


The best answer is “d.” It's estimated that approximately 100,000 cows are killed by lightning each year. This is partly because they spend much of their time outdoors and partly because they have four legs. Statistically, lightning occurs more frequently outdoors, and lightning currents flowing in the ground are more likely to kill four-legged animals than two-legged animals. 

Trees also tend to be located outdoors. When lightning strikes a tree, current spreads radially outward through the ground. Cows are pretty good conductors, so some of the current flowing in the ground will enter the cow through the front legs and exit through the back legs. Breeds that are more conductive, such as Holsteins, tend to be more susceptible to lightning than breeds with a higher electrical resistance (e.g., Guernseys or Brown Swiss). 

Wooden barns can also be a dangerous place for cows during a thunderstorm. Wooden barns with lightning rods direct the lightning currents to the earth under a cow's feet. Wooden barns without lightning rods can burn down. (Another outcome that is not likely to bode well for the cow.) Red barns are a little safer than barns painted other colors. The iron oxide in red paint is static dissipative and reduces the probability that the barn will suffer a direct strike.

Parked cars are relatively safe places for humans to take shelter during a thunderstorm. The metal structure of the car forms a Faraday cage that protects the occupants even in the event that the car is struck by lightning. Unfortunately, it's been well documented (e.g., do an internet search of "cow in a car") that cows prefer convertibles, or they stick their heads out the window. This negates any benefit from the Faraday cage. 

Statistically, golf courses are among the safest places for cows to be during a thunderstorm. While 5% of all human fatalities from lightning occur on a golf course, the rate among cows is less than 0.001%. This is likely due to the flags that tend to draw lightning to the greens. Cows avoid the greens because the grass is not edible, but humans often congregate there.

It's also interesting to note that, in humans, males are four times more likely to be struck by lightning than females. On the other hand, virtually all of the cows killed by lightning are female. Clearly, this is a subject that warrants additional research. 


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