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Why Is the Grass Greener After a Storm?

June is the start of thunderstorm season in Will County. And thunderstorms have a weird side effect. They make grass greener! But how does this work?

(Photo via Shutterstock)

The low down on thunderstorms

At any given moment, about 1,800 thunderstorms are occurring in the world, according to the National Oceanic and Atmospheric Administration. This means that there are about 16 million thunderstorms every year! Of these millions of storms, about 100,000 occur in the United States each year.

Thunderstorms need two basic things to develop: moisture and quickly rising warm air. So it makes sense that we see them the most in spring and summer, especially when it is humid.

Ok, but what does that have to do with green grass? It all comes back to nitrogen! This element is the main thing that makes your grass green.

Earth’s atmosphere is made up different gases. The main gas is nitrogen, which makes up about 78% of the atmosphere. Oxygen makes up about 21% of the atmosphere, and there’s smaller amounts of other gases like argon, carbon dioxide and methane. Unfortunately, grass, like all plants, can’t use pure nitrogen from the air. It must be converted to something else first.

This is where nature comes in. Rain pushes nitrogen into the soil. Microorganisms in the soil — think bacteria and archaea — munch away at the atmospheric nitrogen, changing it into forms of nitrogen that can be absorbed by plant roots. These are called nitrate and ammonium, and this is what makes grass green.

During a thunderstorm, a bolt of lightning can instantly change nitrogen into nitrogen oxide. Grass can absorb this nitrogen oxide instantly from the air without waiting for the microorganisms to do their work. Talk about instant green!

Check it out for yourself!

When it looks like a storm is brewing, check out your grass. What color is it? You can even pick a couple of blades for a closer look. Then wait out the storm from the safety of your home. It shouldn’t take long. Most thunderstorms only last about 30 minutes. Never stand outside during a storm, because lightning is dangerous. It's safe to go outside 30 minutes after you last hear thunder. When the storm clouds pass and are a safe distance away, investigate your grass again. Is it the same color? Pick a couple of blades for comparison.

Explore even further. How does the color of grass look right after rainfall with no lighting? Do other plants change color the same way? Does it turn greener if there is a lot of lightning? Have fun exploring our wonderful world this summer.


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