Today’s Wonder of the Day was inspired by Laura. Laura Wonders, “What are oktas?” Thanks for WONDERing with us, Laura!

If you’ve been WONDERing with us for a while, you may have learned a lot about measurements. Maybe you’ve read about how we measure air pressure, weight, or even time itself. Today, we’re WONDERing about another unit of measurement—the okta!

What does the okta measure? Here’s a hint: It can fly, but it doesn’t have wings. What are we talking about? Clouds, of course! Specifically, the okta measures cloud cover. That’s the amount of the sky covered by clouds at any specific time.

Have you ever watched or listened to a weather report? If so, you may remember hearing words like “partly cloudy,” “partly sunny,” or “mostly cloudy.” Meteorologists pay close attention to how heavy cloud cover is on a given day. That’s because clouds affect the weather, including the temperature and likelihood of precipitation.

How do meteorologists measure using oktas? First, they mentally divide the sky into eight equal boxes. Each of these boxes is one okta. If you think about it, this makes sense. After all, the prefix “octa-” means eight.

Next, they estimate how many of these equal boxes all the clouds in the sky could fill up if they were pushed together. These estimates are rounded up if even part of a box would be filled. The resulting number of oktas help meteorologists communicate the weather to the public.

For example, a measurement of zero oktas means there are no clouds in the sky. This is a clear, sunny day. One okta means the day will be fair, while two- or three-okta days are described as mostly sunny. If the clouds cover between four and six oktas, the day is partly cloudy. A score of seven means mostly cloudy. Of course, eight oktas means the sky has full cloud cover.

Sometimes, conditions are so foggy that meteorologists can’t see the sky well enough to measure cloud cover. In these cases, they give the day a measurement of nine oktas.

Of course, cloud cover isn’t the only measurement that matters. Cloud base measures the cloud’s altitude, and its height is the distance from the cloud base to its top. These measurements also affect how clouds might influence the weather.

Are you interested in clouds? Maybe a future in meteorology would be right for you! It can be fun to learn about the many different factors that affect the weather on a given day.

Standards: NGSS.ESS2.D, CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.W.2, CCRA.W.4, CCRA.W.9, CCRA.W.10, CCRA.L.1, CCRA.L.2, CCRA.L.3, CCRA.L.6, CCRA.SL.1, CCRA.SL.2