Our daily show will pick back up again on Monday, August 15th. All right, let's get to today's current events.

First up, this morning, the Southern and Central parts of Texas were under a flash flood watch.

May was the wettest month in the US state history, but June hasn't brought any relief so far.

Rainfall of more than two inches per hour is in the forecast.

The governor has declared a state of emergency in 31 Texas counties,

and what that does is speed up assistance to the areas that need it most.

The ground is already saturated in many parts of the state,

so a forecast of more rain can only increase the threat of floods. For perspective, last month alone,

Texas got more than 35 trillion, that's trillion with a t, 35 trillion gallons of rain

that would have been enough to cover the entire state with almost eight inches of water,

though the rain was concentrated in specific areas. Where's it all going?

We've already seen the water come up. And actually, the Sheriff Office came by and said,

have you seen the water go down because we think we've crested. No, it hasn't crested yet.

It's still coming up. I'm gonna get out of the way here. You can see behind me, this is the river, river.

We should be talking about a river that's about 200- feet wide. It is well over a mile to the other side.

This is not a boat ramp,

this is an exit ramp from the turn around to go under the bridge and back up onto the highway,

the other direction.

People won't be driving on this for quite some time.

The rain continues in places that have seen now up to 20 inches of rain, just this month.

So, all of these dirt that I'm standing out of here, I'm over kind of on the side, over by a fire ant hill.

Fire ants aren't that happy about this rain neither. But all of this is completely soggy.

Nothing that rains today is gonna soak in. It's just gonna run back off.

This whole place is like a big concrete parking lot. When it rains, it runs off, and these rivers are still coming up.

They will be coming up still four days. This rain doesn't stop until Saturday afternoon, maybe Sunday.

We're watching upstream, because all that water has to run back down right here.

Some residents of the city of Fort McMurray, Canada, have begun returning home.

Last month, the massive wildfire forced the evacuation of 80, 000 people in the area.

Thousands of firefighters are still trying to get a handle on it,

though the blaze is no longer a threat to Fort McMurray.

The fire destroyed about ten percent of the city, at least 2400 buildings or homes.

Not everyone in Fort McMurray is allowed to come back yet.

Authorities say debris from the fire has to be removed before some homes can be occupied.

Many are still intact, but some residents don't know what they'll see.

From Canada, we're moving across the Atlantic to Switzerland, where the longest,

deepest tunnel in the world is now open. It's named the Gotthard Base Tunnel.

It's 35 miles long and runs underneath the Swiss Alps. In some places, it's one and a half miles deep.

And the trains that traverse it hit speeds of up to 155 miles per hour. Will it save time? Yes.

Officials say trains will be able to get from Zurich, Switzerland to Milan,

Italy about an hour faster on this route than trains on other routes. Will it help in other ways?

Yes, officials say freight will be moved more quickly, more efficiently, and more reliably.

What was the cost?

The tunnel took 17 years and $ 12 billion to built, about 2, 600 people worked on it along the way.

Thank you for all of your roll call submissions this school year. We received more than 100, 000 requests.

The last three schools we'll mention start with Avon Grove Charter School.

It's in West Grove, Pennsylvania, the home of the Wolves.

Moving west to Charlotte, Michigan, hello to the Orioles. Great to see everyone at Charlotte High School today.

And in Big Sky country, the community of Big Sky, Montana,

we totally dig the miners of Ophir Middle School.

There are a number of ways scientists can measure air quality.

Monitoring stations can keep track of the air in one specific place and detect any changes.

Trucks loaded with mobile instruments can be sent to different areas,

measuring carbon monoxide and ozone levels.

And satellites can track pollutants and how they move over a city.

There's another way to measure the quality of the air though by flying right through it.

600 hours, NASA prepares to fly. A beautiful sunrise masked by a lingering haze,

one of the reasons this DC- 8 Jetliner is here in South Korea.

This flying laboratory will find out what pollutants are here, who's causing them,

and how they can be measured more accurately from space.

Eight hours flying the length and breadth of South Korea over cities, mountains,

and sea, collecting and analyzing data.

The equipment on this flight may be state of the art, but the plane itself isn't. It's almost half a century old.

It first flew back in 1969, I'm told, as part of the Alitalia fleet. But as you can see,

NASA has completely refitted it to suit its purposes.

25 different instruments for measuring pollution and 34 scientists.

All of them excited to be part of this mission, a joint study with the South Korean Environment Agency.

Well, I don't think it's a discovery, but the air here is pretty dirty.

We kinda knew that.

South Korea has long blamed China for much of its pollution.

So- called yellow dust is known to blow in from deserts in Mongolia and Northern China,

picking up some pretty toxic hitchhikers along the way.

But fine dust particles, very detrimental to your health, may often originate closer to home.

The flight we're on today,

we've seen some of the largest pollution that we've seen the entire campaign,

and most of that is coming from local sources.

To capture some of this data, the plane has to fly low, involving skillful flying from former air force pilots,

and some deft negotiating with air traffic controllers, and a fair dose of turbulence.

It's not everyday you fly just a few hundred feet over the center of a 10- million strong metropolis.

South Korea ranked 173rd out of 180 countries in terms of air quality in a recent study by Yale University.

But this year's environmental performance index underlies the fact it is a global problem,

saying more than 3. 5 billion people, half of the world's population, live in nations with unsafe air quality.

As more than one scientist on board told me,

at least South Korea was acknowledging there's a problem and

opening up its air space to NASA and its expertise.

Paula Hancock, CNN, on board NASA's DC- 8 research jet over South Korea.

We're not gonna run away without a look at, let's call it, lighthearted news, or in this case, light- footed.

Check it out, y'all, a moose on the loose. This happened in Watertown, Massachusetts, earlier this week.

Not too common a sight in the neighborhood.

The wayward mammal didn't really hurt anyone or cause any mischief,

though it did lead police on a 45- minute chase.

Eventually, it moosied over into the woods.

It moosed have realized its moosetake and decided to hoof it. Maybe, it woodsn't having fun in the forest.

It wanted to stretch its mooseles or look for something more amoosing.

But straying into the suburbs probably wasn't the antler.

My name is Carl, and I'm Azuz on the loose.

We'll see you again on August 15th.

Please keep up with us over the summer on Instagram, Facebook, or Twitter.

I'm @ CarlAzuzCNN.

And thanks to the millions of you who've watched worldwide in this extraordinary year

for CNN Student News.