Your phone makes that jarring alarm sound. “Severe Thunderstorm Warning issued for your county until 8:45 PM.” Most people glance at it and keep doing what they were doing. Some people panic. Most people fall somewhere in between and quietly wonder: do I actually need to do anything right now?

Here’s what that alert actually means, how it’s different from a watch, and what families should genuinely do when one hits.

What Makes a Thunderstorm “Severe”

Not every thunderstorm qualifies. A storm earns the label “severe” from the National Weather Service when it produces at least one of these:

  • Wind gusts of 58 mph or higher, strong enough to snap branches, knock over fences, and flip lawn furniture into your neighbor’s yard
  • Hail one inch in diameter or larger, that’s roughly the size of a quarter
  • A tornado, at which point it usually triggers a separate tornado warning on top of the thunderstorm one

Regular thunderstorms with heavy rain and lightning don’t automatically qualify. It’s the extreme wind and hail that push a storm into severe territory.

Watch vs. Warning: The Distinction That Actually Matters

This is the one everyone gets wrong, and it matters because the two require very different responses.

A Severe Thunderstorm Watch means conditions are right for severe storms to develop. The atmosphere has the ingredients, warm, humid air, wind shear, instability, but nothing has happened yet. A watch typically covers a large area (multiple counties or even several states) and can last 4 to 8 hours.

Think of a watch like a weather forecaster saying: “We’ve got groceries for a bad dinner. It might still turn out fine, but keep an eye on the stove.”

A Severe Thunderstorm Warning means a severe storm is happening right now or is minutes away from your location. A meteorologist at the National Weather Service has seen it on Doppler radar or a trained storm spotter has reported it on the ground. Warnings cover a much smaller area and typically last 30 to 60 minutes.

The dinner analogy: dinner is burning. Act now.

A Severe Thunderstorm Emergency is rarer and more serious than either. It’s issued when a storm is producing extremely destructive conditions, baseball-sized hail, winds over 80 mph, and widespread damage is expected. If you hear this one, take it seriously.

How the Warning Gets Issued

It starts with radar. NWS meteorologists monitor weather radar around the clock. When they spot rotation, a strong wind signature, or a hail-producing storm core on the radar, they issue the warning within minutes.

The alert travels to your phone through the Wireless Emergency Alert system, that’s the loud BUZZ that interrupts whatever you’re doing. It also goes to TV and radio stations, NOAA weather radios, and weather apps simultaneously.

The warning includes a polygon on a map showing exactly which area is affected. Your phone’s location determines whether you get the alert. If you’re just outside the polygon, you might not get it even if the storm is close.

What Severe Thunderstorms Can Actually Do

Understanding the real risks makes it easier to take the right action instead of either overreacting or ignoring it.

Damaging winds are the most common severe thunderstorm hazard. Straight-line winds from a strong storm can reach 80 to 100 mph in extreme cases, stronger than a Category 1 hurricane. These winds can uproot trees, take down power lines, and send unsecured objects airborne.

Large hail damages cars, breaks windows, and can injure people caught outside. Hail falls fast, baseball-sized hail can hit the ground at 100 mph. Getting caught outside in a large hail event is genuinely dangerous.

Flash flooding often follows severe thunderstorms because intense storms dump heavy rain in a short time. Six inches of water can knock an adult off their feet. Two feet can carry away a car. Never drive through flooded roads.

Tornadoes can spin up quickly from a severe thunderstorm with little additional warning. A severe thunderstorm warning doesn’t mean a tornado is coming, but it means the conditions that produce tornadoes are present.

What Your Family Should Do

During a Watch

  • Stay aware. Check your weather app for updates.
  • Move your car into the garage if possible.
  • Bring in lawn furniture, toys, bikes, anything that could become a projectile.
  • Know where you’ll shelter if the watch becomes a warning.

When a Warning Is Issued

  • Get inside a sturdy building immediately. Not a shed, not a car (for hail especially), a real building with solid walls.
  • Move away from windows. Flying glass is a major injury risk in high-wind events.
  • If you’re driving, pull over safely and wait it out, don’t try to outrun the storm.
  • Stay off porches and away from trees.
  • Keep watching. Warnings are updated regularly. A storm that seems to have passed can have a second cell right behind it.

With Kids Specifically

Keep the explanation calm and factual. Something like: “The weather service saw a really big storm on radar nearby, so we’re going to stay inside until it passes. It’s just like how we wait inside when a car drives through a puddle, we’re just being smart about it.”

Kids pick up on adult anxiety. If you’re calm and purposeful about getting inside and away from windows, they will be too.

After the Storm

Wait for the warning to expire before going back outside. The official expiration time is in the alert. Don’t assume it’s over because the rain stopped, the strongest winds sometimes hit at the trailing edge of a storm cell.

Once it’s clear, check outside carefully before letting kids run out. Downed power lines, broken branches, and flooded areas are common after severe storms. If a power line is down, stay at least 30 feet away and call 911.

The Takeaway

A watch means stay alert. A warning means take cover. The difference between the two is the difference between “might happen” and “happening now.”

Severe thunderstorms are common in most of the US, especially in spring and summer. Knowing what the alert means and having a simple family plan means you’ll respond well instead of scrambling when the alarm goes off.

For more on how storms develop and why they get so powerful, read our explainer on how storms work. And explore more weather explained posts for kids and parents.