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Squeaks and I are going to the playground tomorrow, but I hope it doesn't rain.  Oh, great idea, Squeaks.  We can use my phone to see what the weather is supposed to be like.  Well, it looks like it's not supposed to rain tomorrow.  I'm glad we checked.  

You might check the weather before you make plans, too, but have you ever wondered how we can tell if it will rain way before it happens?  If you look up at the sky in the morning and see lots of dark clouds, that means it will probably rain that day, but those clouds don't tell you if it will rain tomorrow or the next day.  Sometimes clouds fill the sky or clear up really quickly.  So how does the weather app on my phone tell me if it'll rain next week?  

We know so much about weather, thanks to scientists called meteorologists.  Part of a meteorologist's job is to predict the weather.  They use science to figure out what the weather is probably going to be over the next few days.  They can't say for sure, but they can make a pretty good guess.  To make those guesses, meteorologists do much more than just look up at the sky.  Instead, they use clues they get from lots of different places to figure out what the weather will probably be like.

Some of the clues come from something called radar, a type of tool that can show what's happening in the sky, even things that are far away and would be hard to see with just your eyes.  If you've ever seen pictures or video during a weather report, they come from radar.  Now, to me, the picture looks like a bunch of colored blobs on top of a map, but meteorologists can look at the picture and tell lots of things about the weather.  

For example, the different colors on a radar picture show where it's raining and how hard it's raining.  Green means a little bit of rain.  Yellow means a medium amount, and red means it's raining a lot.  Radar also shows which way the wind is blowing and which way the rain clouds are moving, so even if there are no clouds in the sky right now, if radar shows that some rain is moving toward where you live, there's a good chance you're going to get rain pretty soon.  

That's one clue meteorologists can use to predict the weather.  They can also use satellites, computers we send into space that can take pictures of the Earth.  When meteorologists look at the pictures from satellites, they can see the clouds from above, including which way they're moving and how fast.  That helps them see when storms are forming and predict where the storms will go, so that's another clue.  If a satellite picture shows a storm is heading your way, a meteorologist can tell you that it might rain in a few days.

Now, satellites and radar are pretty amazing tools, but they only provide some of the clues that meteorologists need to predict the weather.  Meteorlogists can also sometimes tell if there will be a storm before there are any clouds.  For example, when a bunch of warm air meets a bunch of cold air, they usually create some clouds and rain when they mix together.  So if a meteorologist sees that there's some warm air and some cold air moving toward each other, they know it will probably rain when the two types of air meet.  

But some of the most important clues that meteorologists use come from something that you can do at home: look for patterns.  A pattern is something that happens the same way over and over again.  So if you live in a place where it was hot in summer and cold in the winter last year and the year before and the year before that, it will probably be the same this year, too.  Meteorologists look at weather patterns all the tim and use the patterns they find as clues when they predict the weather.

Ah, you're right, Squeaks, even with all these clues, weather can change at the last minute, so these predictions aren't always perfect, but they can be pretty close.  So we'll check the weather again in the morning just in case, but let's still plan on going to the playground tomorrow.

Thanks for joining us.  Do you have questions about rain or the weather or anything at all?  We have a website where you can send them to us.  Just ask a grown-up to help you go to Patreon.com/SciShowKids to check it out, and we'll se you next time here at the Fort.

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