AMNA NAWAZ: More than 90 million Americans are under heat advisories this week.

In the West, where a record-breaking heat wave is expected to be long-lasting, firefighters are working to extinguish several major wildfires, forcing thousands of Californians to evacuate.

All of this comes as President Biden unveiled long-awaited regulations designed to protect workers from excessive heat.

Stephanie Sy has more -- Stephanie.

STEPHANIE SY: Amna, many people may not realize it, but heat is the leading cause of weather-related death in the U.S. As many brace for triple digits in the days ahead, protection from extreme heat is top of mind for many.

Hayley Smith is an environmental reporter with The Los Angeles Times and has been covering all this closely.

Hayley, it's good to see you.

It seems every July more heat records are shattered, and yet I have seen a lot of superlative language around what's facing Central and Northern California this week.

Why is this heat wave so concerning?

HAYLEY SMITH, Environment Reporter, The Los Angeles Times: Hi.

I think it's for two reasons.

One is that this is not only a severe heat event, but it's also a prolonged event.

We have got excessive heat warnings, in effect, basically from the far northern counties of California all the way down to the Mexican border.

Portions of the Coachella Valley are going up to 120 degrees, the Sacramento area and the Central Valley up to 115 degrees, even 110 here in some parts of Los Angeles.

And these temperatures really aren't supposed to let up until at least next week, so there's just no chance for people to find any relief.

STEPHANIE SY: Yes, even at night, I understand.

A statement from the National Weather Service's Bay Area office stood out to me, because it says the scale, magnitude, and longevity of this heat wave will likely rival anything they have seen in the last 18 years.

Talk about what the major impacts may be, including wildfire risks.

HAYLEY SMITH: Absolutely.

So, with rising temperatures like this, we see increased risk of wildfires, and that's because the hotter temperatures really dry out the state's landscape and vegetation and just prime it to burn.

So, as you said, we have already seen at least half-a-dozen wildfires popping up around the state this week.

One that we're watching really closely is the Thompson Fire in Oroville, Butte County, which has already burned some structures, injured firefighters, and prompted thousands of mandatory evacuations.

But the other risk of heat, as you referenced at the beginning, is that it is so, so dangerous.

It is, in fact, responsible for more deaths in the United States than hurricanes, tornadoes, and floods combined over the last 30 years.

So there's just something so insidious about extreme heat, and not a lot of people are totally aware yet of how dangerous it can be.

STEPHANIE SY: Absolutely.

And a heat wave in 2022 in California was blamed for hundreds of excess deaths, some 395.

It's been assumed that many of those deaths were heat-related.

Are officials better prepared this year?

HAYLEY SMITH: Yes and no.

I think that officials, in terms of lawmakers, policymakers, emergency responders, are getting better at being aware of the dangers of extreme heat and trying to communicate them to the public.

Here in Los Angeles, for example, we have seen the city activating some cooling centers, where people can just go get some water and some shade and take a break from the heat.

There has also been a lot of information campaigns launched in recent years trying to educate people about the dangers.

But, as you mentioned, that 2022 heat wave killed almost 400 Californians.

There was another heat wave in Phoenix last year where it lasted for 31 days and killed about 645 people.

So the dangers are still very much there.

STEPHANIE SY: Right.

Let's talk about these new workplace rules that the Biden administration has proposed to protect workers from heat-related risks.

What are they, and are they like regulations that California has had in place for years already?

HAYLEY SMITH: Yes, this is such a big news.

OSHA this week has moved forward a proposed rule that would establish indoor and outdoor workplace heat standards for millions of workers, some 35 million workers in workplaces like kitchens and farms and warehouses, where temperatures regularly soar to 80 degrees or hotter.

And so what these regulations would do would be triggering things like employers needing to provide water and rest breaks.

And at 90 degrees, some of those things would become mandatory, mandatory rest breaks and water breaks, things like that.

And, yes, to answer your question, this does mimic some moves that we have made here in California.

We became the first state in 2006 to establish heat standards for outdoor workers.

And just last month, we passed standards for indoor workers.

And it's also important to note that these OSHA -- these proposed OSHA regulations, would also apply to states that have kind of done the opposite, like Florida and Texas, where they have actually passed laws recently to prevent employers or cities from establishing worker protection.

So these federal rules, if they were approved, would supersede that and hopefully help save some lives.

STEPHANIE SY: So, according to the EPA, there are an average of about 34 deaths a year attributable to heat on the job.

Construction workers bear the most risk.

But that still doesn't account for thousands of other heat-related deaths every year nationwide.

What else are officials doing to reduce heat-related fatalities?

HAYLEY SMITH: Yes, you're right.

It's presumed that a lot of these heat death numbers are undercounted.

We know that they're chronically undercounted.

Here in California, we are working on establishing a heat wave ranking system that would actually rank heat waves similar to what is done for hurricanes, so like a Category 5 heat wave, for example.

The state is also working to improve its efforts to surveil and track heat-related illnesses and deaths.

And then, at the federal level, there's actually been a huge push in recent weeks to get FEMA, the Federal Emergency Management Agency, to broaden its definition of a major disaster to include extreme heat, which advocates say would open up new avenues of funding for cities and states that are trying to deal with this worsening issue.

STEPHANIE SY: That is Hayley Smith, an environmental reporter with The Los Angeles Times.

Hayley Smith, thank you.

HAYLEY SMITH: Yes, thanks for having me.