JOHN YANG: Tomorrow morning is the autumnal equinox, the official end of a summer that's been the hottest on record.

A recent report from UNICEF says that around the world, nearly half a billion children live in places where they've been at least twice the number of 95 degree or more days than there were in the 1960s.

The report says extreme heat creates health concerns for children and for pregnant women.

It increases the likelihood of stillbirths, babies with low birth weight and premature births.

Lily Caprani is UNICEF's chief of Global Advocacy.

Lily, are there places in the world where this problem is especially pronounced?

LILY CAPRANI, Chief Global Advocacy, UNICEF: Well, as you've said, this has been the hottest summer on record, and that's affected every country in the world, including in the United States in Western Europe, but there are some countries that have had it particularly bad.

Some of the countries in West and Central Africa that UNICEF has been studying and researching the temperatures of have had as many as four whole months back to back of extremely hot days over 95 degrees Fahrenheit, children who are living through extreme heat for huge portion of the year now, but it's affecting every country in the world.

JOHN YANG: And what are the effects that we see, especially in children?

What effects show up?

LILY CAPRANI: Yeah, the reason UNICEF is worried about this with the UN children's agency, we see that children all over the world are really struggling with the extreme heat.

I mean, it affects all of us.

It affects older people and young people, especially badly for young children, especially very young babies and infants, their bodies are particularly vulnerable to the effect of heat stress, because they're not just like little adults.

Their bodies work differently.

They get hotter more quickly.

It takes more for them to try and cool their bodies down.

Anyone who's held a baby in their arms will know their hearts beat twice as fast.

They breathe more quickly.

They tend not to be able to sweat very well.

And all of these things add up to making them quite vulnerable to the effect of extreme heat, and it can attack their body much more quickly.

So it's a worry for anyone who's a parent, a grandparent, someone who's looking after children in healthcare facilities, that this kind of extreme heat poses a significant threat to the health of young children.

JOHN YANG: And as we pointed out in the introduction, it was also in your report, this also has effect on pregnant women.

What affects them, particularly about this?

LILY CAPRANI: Yeah, extreme heat, when you exposed over time as a pregnant woman is actually associated with lower birth weights.

Premature births can really affect the health of a pregnancy, that affects the mother, and of course, the young unborn baby, especially if they're born preterm.

So there's a lot of associated risks of being exposed to extreme heat, and we know it's happening more often.

These periods of extreme heat are lasting for longer, and they're getting more and more intense as each year goes by.

JOHN YANG: Does this also have an effect on food production, on drought that affects children?

LILY CAPRANI: Yeah, when we think about extreme heat and heat stress, the first obvious thought is about your health, your physical health, but actually the knock on effects are much broader than that, especially for children.

So, if there's very extremely hot days for a long period, it can affect their schooling.

Can they concentrate?

Is it too hot to learn?

Can they even keep the schools open?

And then there's the other effects on the environment around them, especially in countries that maybe don't have the infrastructure, the cooling infrastructure, like air conditioning, or where there's already kind of lots of pressures on the land.

Maybe there's drought, scarcity of clean water, and it can affect food production crops, and that has a big knock on effect on children's not just their learning and their health, but their diets and the prospects for the future.

JOHN YANG: You talk about infrastructure, we think of the United States as being a advanced, wealthy nation, but you say this is also affecting children here in the United States.

LILY CAPRANI: We know that the planet is warming and it doesn't respect borders, right?

So every country is having more heat waves every year.

It's getting hotter and hotter, and the United States is affected.

We know actually, that at least half of the children in the United States are experiencing double the number of heat waves compared to what their grandparents' generation lived through.

So no one escapes this.

We're all in this together.

There are heat trapping gasses that are warming this planet.

There are some practical things we can do to protect children, and we must do to protect children right now, but in the long run, we're going to have to bring down those temperature rises if we want to stop this getting worse.

JOHN YANG: Talk about those short term things you can do right now.

LILY CAPRANI: So anyone who's a parent, a carer, or works with children needs to be aware of the risks to their health, well, to everyone's health, but particularly vulnerable, younger children.

And something you can do if you're a parent and your child is old enough to understand is explain to them to look out for the signs of heat stress, like if it is a really hot day, make sure you stay hydrated.

Drink a lot of water, even if you're not feeling thirsty, keep drinking water.

Keep yourself hydrated.

Take yourself out of the hot place if you can, try to cool down.

If your child appears to be suffering from heat stress, they seem maybe dizzy, confused or feeling a bit nauseous, it's really important to cool them down as quickly as possible.

And if it seems like it's not working, get medical attention.

It can be serious and it can escalate really quickly.

And then all of the services that care for children, whether it's teachers in the classroom, whether it's doctors, nurses, they can also do a lot to help care for children in these situations, try and prevent it happening, be more aware of the risks, because we'll all have to become more and more aware as it keeps happening every year.

JOHN YANG: Lily Caprani of UNICEF, thank you very much.