Boom! Thunderstorm FAQ in the forecast

This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.


SEATTLE- The rumble of thunder is something we don’t often hear in Western Washington. But, today is one of those exceptions.  So we’ll do a question and answer with Q13 Meteorologist Tim Joyce.

What is a thunderstorm?

A thunderstorm is a storm that has lightning and thunder. It is produced by a cloud called a cumulonimbus. These often come with gusty winds, heavy rains and sometimes even some hail.

What causes thunderstorms?

The basic ingredients you need to create thunderstorms are moisture, unstable air and lift. The moisture is needed to form clouds. The unstable warm air causes rapid rises in the atmosphere and the lift can from  fronts, sea breezes or most often here in the Pacific Northwest the lift comes from the mountains. Often you’ll see towering clouds in the Cascades or Olympic mountains in the summer while it’s nice and sunny around Puget Sound lowlands.

When are thunderstorms most likely to occur?

Thunderstorms can occur any time of year and at any hour of the day when all the ingredients are in the right amounts. In the Pacific Northwest, they occur most often in the spring and then sporadically in the fall, summer– and very infrequently in the winter. The mostly likely time of day for thunderstorms is in the afternoon and evening hours when temperatures (and solar energy) tends to peak.

Are thunderstorms dangerous?

Yes, very dangerous. Every thunderstorms produces lightning, which kills more people each year than hurricanes or tornadoes. If you hear thunder, you are close enough to be struck by lightning. The Nat’l Weather Service says about 50-100 people die in the U.S.  every year from being struck by lightning. The most dangerous activity for being struck by lightning is not golfing, it’s actually fishing/boating. The catchy phrase the Nat’l Weather Service wants you to remember is “when thunder roars, go indoors.” But even some inside activities are dangerous during thunderstorms. Since water is such a great conductor of electricity, avoid taking showers or baths.

What causes lightning?

Lightning is an electric current. Within a thundercloud, frozen raindrops bump into one another as they move around in the air. All of these collisions create an electrical charge. Picture yourself in fuzzy socks dragging your feet around the carpet in your living room. When the clouds is filled up with electrical charges it has to go somewhere. The lightning discharged between parts of the cloud or between the cloud and ground is pretty much the same thing as when you touch a doorknob– except on a MUCH bigger scale. It’s estimated a lightning strike is hotter than the surface of the sun.

What if I want to know where lightning is right now?

You can always check out this website to see where lightning is anywhere in the lower 48 states:   But, we have a great new tool you can check out on your smart phone. Download the Q13 Weather App in the Apple Store or Google Play and you can see where lightning is in your neighborhood– and it will even alert you when lightning is detected within a few miles. It’s a great feature to have when you’re living a busy Northwest outdoor lifestyle.

Can you really use thunder to tell how far a storm is?

Sort of, yes. Because lightning travels at the speed of light– and thunder travels at the speed of sound, you can figure out how far away the most recent lightning strike was. Keep in mind these storms could be moving towards you or away from you– so it’s best to do it several times. Count the number of seconds between seeing the lightning and hearing the thunder and then divide that number by 5. That will tell you roughly how far away it is in miles. So if you counted 15 seconds between the lightning and thunder, the lightning would be three miles away.

What is hail?

Hail doesn’t necessarily have to come with a thunderstorm. Hail comes from any storms with strong updrafts. If you get high enough in any storm, rain is actually frozen water droplets. Hail stones are formed by water droplets that get suspended in the strong winds and freeze over and over again. Each time the hail stone goes up it gets more water on them and then re-freezes high in the storm. Eventually, they will become too heavy to be lifted any more and they fall out of the cloud to the ground. Most of our hail in the Pacific Northwest is pretty small (like the size of tiny gravel). Compare that to the size of giant Midwestern thunderstorms that have incredibly strong updrafts that can produce hail stones the size of golf balls or sometimes even baseballs.

What do I do if I’m caught outside in a thunderstorm?

Of course, the best place to be in inside in a sturdy building, but if that’s not available– a car is a good second spot to seek out. The tires provide insulation so that even if the car was struck, the lightning would go around you through the frame of the vehicle. Here are some tips from the Nat’l Weather Service:

  • Avoid natural lightning rods such as a tall, isolated tree in an open area.
  • Avoid hilltops, open fields, the beach or a boat on the water.
  • Take shelter in a sturdy building. Avoid isolated sheds or other small structures in open areas.
  • Avoid contact with anything metal—tractors, farm equipment, motorcycles, golf carts, golf clubs, and bicycles.
  • If you are driving, try to safely exit the roadway and park. Stay in the vehicle and turn on the emergency flashers until the heavy rain ends. Avoid touching metal or other surfaces that conduct electricity in and outside the vehicle.