Horses and Lightning Safety: When to Stop Riding, Where Not to Tie

What happened at the Jockey Club in San Isidro

Horses and lightning safety comes down to two rules: stop riding at the first thunder, and never leave a horse tied to a wire fence, metal rail or cable during a storm. Argentina got a painful reminder of why this week. On the morning of Wednesday, October 21, 2026, a sunny sky darkened within minutes over the Jockey Club grounds in San Isidro, north of Buenos Aires, where polo is played on fields in the middle of the racetrack.

According to La Nación, four polo mares were tied to a post on field 6, waiting to start a practice. Lightning struck a steel cable nearby, and the discharge killed all four instantly.

Some details, such as who owned the mares and whether anyone at the field was hurt, differ between reports, so we stick to the core facts. What matters for every rider is the pattern: horses tied in a line, metal close by, and a storm that built faster than anyone expected. That pattern repeats across the world every storm season.

Can horses get struck by lightning? How it actually hurts them

Yes, horses can get struck by lightning, and because they are big animals standing in open places, they are more exposed than people. But the Merck Veterinary Manual says the most common way lightning injures animals is not a direct hit: it is current spreading through the ground away from the strike.

Here are the main ways lightning reaches a horse:

• Ground current. When lightning hits the ground, a tree or a pole, the current fans out through the soil, especially wet soil. A horse's four feet sit far apart, so current can flow in one leg and out another.
• Metal that carries it. The National Weather Service (NWS) notes that metal doesn't attract lightning, but lightning can travel long distances through it. Wire fences, cables, pipes and metal rails can carry a strike to a horse that is touching or standing next to them.
• Side flash. Part of a strike can jump from a tree or post to a horse standing close to it.
• Direct strike. It happens, especially to a horse alone in an open field, but Merck ranks it behind ground current and side flash.

Why groups of horses die together

Merck notes that few livestock problems kill several animals clustered in one small area the way lightning does. Animals found under a tree, near or hanging through a wire fence, or bunched around a light pole are classic signs.

A well-known case shows how this works. In 2005, TheHorse.com reported that 16 horses died in one pasture in Calhan, Colorado, after an October storm; 11 were found within a 20- to 25-yard radius believed to be the center of the strike, and four were in direct contact with the barbed wire fence. Another 44 horses in the same pasture were unharmed.

Horses crowd together when weather turns, and tied horses can't move at all. That's why a line of horses tied at a palenque or a rail is so vulnerable.

Riding in a thunderstorm: when to stop

The rule is simple: when thunder roars, go indoors. The NWS says that if you can hear thunder, even a distant rumble, lightning is close enough to be an immediate threat. Lightning can strike as far as 10 miles (about 16 km) from any rain, and many lightning deaths happen before the rain arrives or after it seems to have passed.

For riders, that means:

1. Check the forecast before you tack up. If thunderstorms are forecast, the NWS advice is to consider postponing outdoor activities.
2. Watch the sky while you ride. Towering clouds, a sudden dark sky or a distant flash are your cue to head in, not to finish the set.
3. Call it at the first thunder. Don't wait for rain, and don't wait for the storm to be overhead.
4. Wait 30 minutes after the last thunder before anyone goes back out to ride, practice or move horses.

For polo, lessons and shows

The NWS says anyone running an organized outdoor activity needs a lightning safety plan. For a polo practice, a riding school or a show, decide ahead of time:

• Who has the authority to stop play, and the signal everyone recognizes.
• How long it takes to untack and move every horse, and where they go.
• Where the riders, grooms and spectators shelter.

If moving the whole string takes 20 minutes, you need to start well before the storm arrives. The San Isidro storm built in minutes, so a plan that depends on seeing rain first is not a plan.

Where to put tied or tacked-up horses in a storm

The hardest moment is when horses are tied, saddled or in the middle of a practice. Here is where they should and shouldn't be.

Practical steps when a storm is coming:

• Never tie horses to a wire fence, steel cable or metal rail to wait out a storm, and never leave a line of horses tied in the open.
• Get horses into a substantial building early. If they will be turned out instead, remove saddles and bridles first and use a paddock away from wire fences, lone trees and water.
• Don't stand in the open holding horses. Sheds, open-sided shelters and tents don't protect people, according to the NWS. People belong in a fully enclosed building or a hard-topped vehicle with the windows closed.
• Spread out if you are caught outside. The NWS advises groups of people to spread out, to avoid multiple injuries from one strike.
• If a horse gets loose, let it go until the storm passes. Our guide to catching a loose horse covers what to do afterward.

For paddock shelters, hail and the after-storm walk around fences and water, see how to protect horses from hail. For children at the barn, our horse safety for kids guide covers the basics, and the safety section has more.

Signs a horse near a strike needs the vet right away

Some horses that are near a strike get knocked down and stand up again. That doesn't mean they are fine. Equine practitioner Dr. Doug Thal's Horse Side Vet Guide lists a horse that was hit by or near a lightning strike as an emergency: call your vet right away, even after hours.

Call the vet immediately if you see any of these after a storm:

• A horse that is down, can't get up or struggles to rise
• Stumbling, wobbling, a stunned look or a head tilt
• Bumping into things or other signs it can't see
• Fast, noisy or difficult breathing
• Singed hair or burn marks
• Lameness, trembling or a horse that flinches when touched
• Any horse that was in the group near the strike, even if it looks normal

Merck notes that some effects, including nerve damage and breathing problems from swelling, can appear or persist after the first shock. Leave the exam and treatment to your vet; your job is to keep everyone safe and describe what you saw.

People come first. A person struck by lightning carries no electrical charge and needs help right away, so call emergency services; the NWS also reminds rescuers that lightning can strike twice. Keep your vet's number saved and a stocked first aid kit at the barn.

What to do now, and what to watch next

Storm season is just starting in Argentina, Uruguay, southern Brazil and much of South America. Use a calm day to set your plan:

• Walk your barn or club and mark every wire fence, metal rail, cable and lone tree where horses usually wait or get tied.
• Move the tie-up spot if it sits next to a cable or wire.
• Agree on the rule: first thunder stops the ride, and nobody goes back out for 30 minutes after the last one.
• Time it: practice how long it takes to untack and bring every horse into the barn.
• Save your vet's number in every rider's and groom's phone.

In San Isidro, watch for the club's response, any changes to how horses wait on the polo fields, and official storm alerts in the days ahead. For more on horse care year-round, browse our health basics.