Crouch During Lightning? Water for Heatstroke? 4 Cases Where Official Safety Advice Disagrees
TL;DR
- The US National Weather Service says that if you can hear thunder, lightning can reach you and crouching outdoors does not make you safer, while South Korea's Ministry of the Interior and Safety teaches the 30-30 rule and getting low in a dry hollow.
- The CDC says a heatstroke victim should get nothing to drink and that heatstroke skin can be dry or damp, while Korea's ministry describes it as dry because the person is not sweating.
- Once shaking stops, Korea's ministry says to cut off the electricity and gas, while Ready.gov gives gas shutoff steps for when you smell gas or hear a leak.
- On a Korean expressway the law requires a warning triangle behind a broken-down car, while the UK Highway Code advises never to use one on a motorway.
How many days could your home hold out?See Safe-Life Official safety pages do not always agree, and the gaps show up in the moments that matter: caught outside in a thunderstorm, kneeling next to someone with heatstroke, opening the door to an exit after an earthquake, or stopped on a fast road. South Korea's Ministry of the Interior and Safety (MOIS) publishes action guides for its residents on the Korea Safety portal (국민안전24), and on several points they differ from the US National Weather Service, the CDC, Ready.gov and the UK Highway Code.
I make Safe-Life, a disaster preparedness app, and I ran into these differences while checking its guides against their sources. This post quotes each agency side by side, says which source each line comes from, and shows which side the app's guides now follow.
Lightning: the 30-30 rule and the crouch
The US National Weather Service (NWS) uses the sound of thunder itself as the signal.
- "If you hear thunder, lightning is close enough to strike you." As soon as you hear it, go to "a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up." Its lightning safety page sums it up as "When Thunder Roars, Go Indoors."
- Its myths page lists "If you're caught outside during a thunderstorm, you should crouch down to reduce your risk of being struck" as a myth and answers: "Crouching doesn't make you any safer outdoors. Run to a substantial building or hard topped vehicle."
The MOIS lightning guide says something different:
- If lightning is forecast, stay in, and if you are outside, shelter in a car, a building or underground.
- Keep the "30-30 lightning safety rule": if thunder sounds within 30 seconds of a flash, take shelter at once; wait about 30 minutes after the last thunder before moving.
- Outdoors during lightning, if you heard thunder within 30 seconds, "quickly take shelter in a safe place, immediately get low and move into a dry hollow or a cave," and "it is good to be on an insulator about 10 cm (4 in) or more above the ground" (my translation).
The 30-30 rule is not a Korean invention. A 2005 American Meteorological Society conference paper records that the Lightning Safety Group, a panel of scientists, engineers and medical staff convened in 1998 to standardize lightning safety advice, recommended it: seek shelter if the flash-to-bang delay is under 30 seconds, and wait at least 30 minutes after the last thunder.
Current NWS safety pages do not ask you to count before deciding. Its page on thunder explains that thunder takes about 5 seconds to travel a mile, so counting the seconds and dividing by 5 gives the distance, but adds that "you should be in a safe place while counting." Thirty seconds is about 6 miles (10 km), and the NWS myths page says "bolts from the blue" can strike 10 to 15 miles from the thunderstorm. The rule the NWS gives instead is the plain one: if you can hear thunder, you are close enough to be struck.
The two agencies do share two points: wait about 30 minutes after the last thunder (the NWS says at least 30), and never shelter on a rocky peak or under a lone tall tree.
The NWS stresses that no place outside is safe in a thunderstorm. If shelter is far away, its safety tips say to get off hills and ridges, avoid isolated trees and rock overhangs, get away from water and from wire fences and power lines, and never lie flat on the ground; its myths page adds, "If you are caught outside in a thunderstorm, you keep moving toward a safe shelter."
Heatstroke: does sweating rule it out, and can they drink?
Three sources describe heatstroke a little differently.
| MOIS heat wave guide | US CDC | MedlinePlus (all heat illness) | |
|---|---|---|---|
| Skin | "Hot, dry skin because the person is not sweating" (my translation) | Hot, red, dry or damp | Sweating may stop at this point |
| Body temperature | Above 40°C (104°F) | 103°F (39.4°C) or higher | Above 104°F (40°C) |
| What to do | Call 119 (Korea's emergency number) at once; move to a cool place, wet the skin and fan; ice packs on the neck, armpits and groin | Call for emergency help (a medical emergency); move to a cooler place; cool cloths or a cool bath | Call for emergency help for heatstroke symptoms, a fever over 102°F (38.9°C) or reduced alertness; lie down in a cool place, wet cloths and a fan, cold compresses on the neck, groin and armpits |
| Drinks | None listed for heatstroke; in its heat illness table, water is listed for heat exhaustion, heat cramps, and heat syncope (fainting) when the person can communicate | "Do not give the person anything to drink." Sipping water is for heat exhaustion | If alert, sips of a sports drink, half a cup (120 mL) every 15 minutes |
The table carries most of the answer. Two notes on what it does not show: MedlinePlus covers everything from heat cramps to heatstroke in a single first-aid list, which is why its "if alert" drink advice sits next to heatstroke, while the CDC treats heatstroke on its own. And because the CDC lists damp skin among the signs, someone who is still sweating can have heatstroke.
All three list calling for emergency help and cooling the person when heatstroke is suspected.
After an earthquake: cut the gas right away, or when it leaks?
During the shaking, the advice matches. Ready.gov, run by FEMA, teaches Drop, Cover and Hold On, and MOIS says to get under a table, protect your body and hold on to its legs. The difference comes after the shaking stops.
| MOIS earthquake guide | Ready.gov | |
|---|---|---|
| During shaking | Under a table, protect your body | Drop, Cover, Hold On; "If you are inside, stay and do not run outside" |
| When it stops | "Once the shaking stops, cut off the electricity and gas and open the door to secure an exit" (my translation) | "Be ready to Drop, Cover and Hold On if you feel an aftershock" |
| Leaving the building | Use the stairs and move quickly to a wide open space such as a sports ground or park | "If you are in a damaged building, go outside and quickly move away from the building" |
| Gas | Cut off once shaking stops | No gas step on the earthquake page; its safety skills page says that if you smell gas or hear a blowing or hissing noise, open a window, get everyone out and turn off the gas at the outside main valve if you can |
The Korean guide does not make the gas step depend on signs of a leak: shutting off electricity and gas is simply the next step after the shaking stops. In Korea that guide is the local standard. In the US, Ready.gov has you stay inside, leave if the building is damaged, and turn off the gas when you smell gas or hear it leaking.
Broken down on the expressway: put out a warning triangle?
In Korea it is the law. Article 40 of the Enforcement Rule of the Road Traffic Act, which implements Article 66 of the Act, says that when a car cannot be driven on an expressway or a motor-vehicle-only road, the driver must set up a warning triangle, and at night also "a red flash, electric light or flare signal visible from 500 meters in every direction" (my translation), placed where drivers approaching from behind can see it. The article gives no distance from the car.
The Korea Expressway Corporation's own safety campaign, as described in a 2024 article by a citizen policy reporter on the government's Korea.kr site, teaches a different sequence: hazard lights on, open the trunk, get out of the car to safety, then call. A triangle is not one of its steps, and the article closes by reminding readers to get behind the guardrail first.
The UK Highway Code advises against triangles on motorways. Its introduction says legal requirements are marked "MUST" or "MUST NOT"; the lines below use advisory wording.
- On other roads (Rule 276), put a warning triangle at least 45 metres (147 feet) behind the car and take great care placing and retrieving it, "but never use them on motorways."
- On motorways (Rule 277), "DO NOT place a warning triangle on the carriageway." If you can get out safely, keep well away from the car and traffic and "get behind a safety barrier where there is one." If you cannot reach the left lane or a place of relative safety and get out safely, stay in the car with your seat belt and hazard lights on and call 999.
What changed in Safe-Life's guides
In the app's 2.2.0 update I checked the guides an earlier review had not reached against official sources and revised over 200 of them. Here is how the English guides on these four topics changed, quoted from the guide data of both versions.
| Topic | Up to 2.1.0 | 2.2.0 (current) | Follows |
|---|---|---|---|
| Lightning (2 guides) | One titled "The 30-30 Rule for Lightning"; the other: "Move to a hollow or low area and crouch down." | Retitled "When Thunder Roars, Go Indoors"; the other: "Crouching does not make you safer, so keep moving toward safe shelter." | US National Weather Service |
| Heatstroke signs | "Heatstroke victims have hot, red skin, no sweat, and are confused or unconscious." | "Heatstroke: body temperature of 103°F (39.4°C) or higher; hot, red skin that may be dry or damp; fast, strong pulse; confusion or passing out." | US CDC |
| Heatstroke drinks | "Provide water or sports drinks in small sips only if the patient is conscious." | "Do not give the person anything to drink, even if they are conscious." | US CDC |
| Earthquake | "Once the shaking stops, turn off the gas and open the front door to secure an exit." | "Once the shaking stops, turn off the electricity and gas and open the door to secure an exit." | MOIS (electricity added to match its current guide) |
| Expressway | No triangle; "Evacuate passengers to the safe area behind the guardrail before calling for help." | "Watching the traffic carefully, set up a warning triangle behind the car, and at night a flare as well." | Korea Expressway Corporation sequence (Korea.kr article) with the triangle step added for the Enforcement Rule |
I chose the NWS for lightning because it rebuts the crouch directly as a myth, and the CDC for heatstroke because it gives heatstroke its own, more specific advice. For the earthquake I kept MOIS's guide, and for the expressway I added the warning-triangle step the Enforcement Rule requires, since the app's guides are written for people in Korea.
Sources
All opened on October 19, 2026. This post compares published guidance; it is not medical or legal advice. App quotes are from the English guide data of Safe-Life 2.1.0 and of 2.2.0, the version now on Google Play. I translated the quotes from Korean pages.
- Lightning Tips - US National Weather Service: where to go when you hear thunder, 30 minutes after the last thunder, last-resort tips outdoors
- Lightning Myths - US National Weather Service: the crouch and lying-flat myths, keep moving toward shelter, strikes 10 to 15 miles from the storm
- Lightning Safety - US National Weather Service: "When Thunder Roars, Go Indoors"
- Understanding Lightning: Thunder - US National Weather Service: 5 seconds per mile, counting in a safe place
- On the Need for Electric-Field Meters to Support Critical Lightning Hazard-Warning Decision Processes - Beasley et al., American Meteorological Society conference paper (2005): the 1998 Lightning Safety Group and the 30-30 rule
- Lightning action guide (낙뢰 국민행동요령) - Korea Ministry of the Interior and Safety: 30-30 rule, getting low in a hollow, 10 cm insulator
- Heat wave action guide (폭염 국민행동요령) - Korea Ministry of the Interior and Safety: signs and first aid for heatstroke, heat exhaustion, heat cramps and heat syncope
- Heat-Related Illnesses: What to Look For, What to Do (2017) - US CDC (CDC Stacks): heat exhaustion and heatstroke signs and steps, nothing to drink for heatstroke
- Heat emergencies - MedlinePlus, US National Library of Medicine: heatstroke signs and temperature, first aid, when to call for help
- Earthquakes - Ready.gov: stay inside, aftershocks, leaving a damaged building
- Safety Skills - Ready.gov: when to shut off natural gas
- Earthquake action guide (지진 국민행동요령) - Korea Ministry of the Interior and Safety: during and after shaking, electricity and gas, open spaces
- Enforcement Rule of the Road Traffic Act, Article 40 - Korea Law Information Center: warning triangle, night signal, placement
- "고속도로 교통사고, '비트박스' 기억하세요" - Korea.kr policy news (July 31, 2024): the Korea Expressway Corporation's hazard lights, trunk, get out, call sequence
- The Highway Code: Introduction - UK Government: only "MUST" rules are legal requirements
- The Highway Code: Breakdowns and incidents (275 to 287) - UK Government: triangles 45 m back on other roads, never on motorways, behind the barrier, staying in the car