Kendra Pierre-Louis: For Scientific American’s Science Quickly, I’m Kendra Pierre-Louis, in for Rachel Feltman. You’re listening to our weekly science news roundup.
If you live in much of California or the southwestern U.S., you’ve likely been muttering to yourself, “it’s hot in here.” Last week a heat dome that centered on that region but that was expected to expand as far east as Mississippi and as far north as southern Montana created unprecedented mid-March temperatures that teetered into the triple digits in some places.
To demystify this early heat wave and its links to climate change, we have Andrea Thompson, senior desk editor for life sciences here at SciAm.
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Thanks for joining us, Andrea.
Andrea Thompson: Thanks for having me.
Pierre-Louis: So spring just started, and much of, like, the Southwest and parts of the western U.S. are cooking; they’re baking. What’s going on?
Thompson: Yeah, so, you know, this is following on a, a March that has been really wild weather-wise in general. You know, March is the beginning of spring, so this is a transitional weather season anyway as the sun comes up and the jet stream over the U.S. kind of shifts. So you have warm and cold air masses colliding—you get things like tornadoes and extreme weather, which we’ve seen.
What’s happening here is: this is an area of high pressure, or a ridge in meteorology speak, and it is incredibly intense, especially for March. And when you have these ridges, temperatures just skyrocket.
So this is an incredibly huge and incredibly extreme and an incredibly persistent heat event, especially for this time of year.
Pierre-Louis: So we know with heat events, there are kind of two big problems, right? One is the heat itself—like, 100 degrees [Fahrenheit, or about 37.8 degrees Celsius] is just 100 degrees. But if you’re coming from a period where it’s maybe not been so hot and you’re now being slammed with 100 degrees, the body really struggles to adapt.
Thompson: Right, the body acclimates as temperatures gradually warm through spring, and then you get into summer. Whereas right now we’re basically plopping summer down right at the end of winter [Laughs], and bodies aren’t ready for that.
Pierre-Louis:  So there really is a risk that, you know, some people might get quite ill or even die from this heat wave.
Thompson: Yeah, there’s definitely that potential, and there are heat advisories and extreme heat warnings out in some places, you know things like that.
Pierre-Louis: This is all happening also at a time where much of the West, I believe, is dry. So what is this combination of very hot weather and already somewhat dry conditions going to do?
Thompson: A lot of the West, in particular, you know, in the Rockies, has been pretty dry this winter, and it’s been a very warm winter. In fact, western U.S. has more distinct wet and dry seasons, and they depend a lot on snowpack that builds up during the winter and gradually melts in spring and summer. But there’s not [Laughs] a lot of snowpack left already ’cause it’s been so warm, and a lot of what precipitation fell this winter fell as rain. What snowpack is left, a lot of that’s gonna get melted out by this event. And the ground and rivers may not always be able to absorb all of it, so some of that’s going to be lost.
So you’re setting up, you know, a drier spring and summer, which makes the potential for a really bad wildfire season a lot higher. The biggest wildfire in Nebraska’s history is, is happening there right now. So, you know, there’s a big concern, and especially in some of the higher mountain forests that we haven’t seen a ton of wildfire activity in the last few years, that that could change with things being so dry and the snowpack so low.
Pierre-Louis: So that naturally raises the question of climate change. Kind of how does that factor into everything that we’re seeing?
Thompson: So at the very basic, climate change means that when you have a big heat event, it’s going to be hotter than it was in decades past because the sort of baseline temperature of the Earth is higher. So it’s sort of—it makes the extremes more extreme.
There’s some evidence that you can have these sort of “weather whiplash” events in the West, where you go from a period of kind of relative moisture to one of extreme dryness pretty quickly. And that’s bad for wildfires because you’ve built up this very green [Laughs] grasslands and forest, and then all of a sudden, it dries out and there’s more fuel for fires.
And what’s really interesting is some of the other weather that’s been happening: There was a big, huge blizzard in the Midwest. We had some tornadoes. And out in Hawaii, they had what’s called a “Kona low,” which is a low-pressure system. It brought a ton of rain and flash flooding to the islands. That is actually strengthening this heat event, which is just a fascinating way that these weather events you wouldn’t think are connected can be connected.
Pierre-Louis: We move on from the heat wave to policy changes on childhood vaccines.
Last Monday a federal judge issued a ruling that, at least for now, blocks the Centers for Disease Control and Prevention’s January decision to alter the childhood vaccine schedule. The agency had slashed the number of diseases it recommended kids get vaccinated against from 17 to 11. Among the vaccines the agency removed were those protecting against hepatitis A and B, rotavirus and RSV.
The ruling comes in a lawsuit filed by the American Academy of Pediatrics, along with several other plaintiffs, against the U.S. Food and Drug Administration, the CDC, the National Institutes of Health and the U.S. Department of Health and Human Services. Health Secretary Robert F. Kennedy, Jr., and other officials are also named defendants.
The plaintiffs, who originally filed in July 2025, allege that the defendants’ actions, quote, “sow confusion and undermine public health, purposefully disregard and contravene required process, and ignore decades of established science.” Specifically, the lawsuit points to actions such as narrowing recommendations for the COVID-19 vaccines as well as the mass firing of members of the Advisory Committee on Immunization Practices, or ACIP. In doing so, the plaintiffs say the agencies and officials violated the Administrative Procedure Act, which dates back to 1946 and controls how federal agencies develop and issue regulations.
The ACIP is traditionally a nonpartisan, science-backed, independent federal advisory committee tasked with making recommendations on vaccines. In June the HHS removed the 17 sitting members of ACIP. Many of the members who the health secretary picked to replace them either do not have a background in vaccines and immunology and/or are vaccine critics. The HHS also bypassed ACIP with its January decision to overhaul the childhood vaccine schedule.
In his ruling last week, a federal court judge concluded that removing the previous ACIP members and bypassing the committee in making the new vaccine recommendations had, quote, “undermined the committee’s integrity.” The judge added that the government’s failure to consult ACIP represented, quote, “an abandonment of the technical knowledge and expertise embodied by that committee.”
The ruling blocked the appointments of the 13 members of ACIP who were selected by the HHS secretary, saying the move likely violated federal law.  As a result, the ACIP meeting originally scheduled for last Wednesday and Thursday was postponed.
Continuing on with the theme of children’s health, anyone who has spent time around small kids knows that items—toys, other people’s hands, articles of clothing—have a way of ending up in their mouths. Research being presented at this week’s spring meeting of the American Chemical Society suggests that when it comes to children’s fast fashion, this could be especially concerning. That’s because all of the kids’ shirt samples the presenters tested exceeded the federal limits for lead in children’s products.
The limits exist because lead is a neurotoxin that can severely damage a child’s nervous system, especially if they’re exposed before the age of six. Exposure can cause cognitive impairment, behavior problems, and delayed speech and development.
The researchers, led by Kamila Deavers at Marian University, sampled 11 shirts—all of which exceeded the allowed limit for lead of 100 parts per million. More brightly colored shirts like red and yellow tended to have higher levels of lead. According to the researchers, lead acetate is sometimes used as a cheaper way to help dyes stick to fabrics.
The researchers also simulated what would happen if a child sucked or chewed on the fabric and found that the exposure would exceed the safety limits on lead consumption set by the FDA.
This is not the first study of its kind. A 2025 report by Greenpeace Germany looked at clothing items, including some children’s clothing, from the fast-fashion retailer Shein. It found items that exceeded safety limits in lead, along with other hazardous chemicals. But this latest work zeroed in on children’s clothes without focusing on any one retailer.
And finally, let’s head up to space.
Last Tuesday, SpaceX crossed the threshold of having some 10,000 satellites in low-Earth orbit. The company, which launched its first Starlink satellites in 2019, now accounts for more than 60 percent of the satellites in orbit, but competitors are nipping at its heels. Amazon Leo is planning to launch more than 7,500 satellites, while Chinese government–backed companies Guowang and Qianfan are aiming for 13,000 and 15,000 satellites, respectively.
SpaceX’s satellites have helped some 10 million users connect to the Internet in areas as far-flung as rainforests and battlefields. But it comes with a cost: the night sky. Interference from satellites is already hindering astronomy as celestial objects become harder to see, a situation that will only deteriorate as more satellites take up space in orbit.
That’s all for today! Tune in on Wednesday when we dig into how artificial intelligence may change pure math.
Science Quickly is produced by me, Kendra Pierre-Louis, along with Fonda Mwangi, Sushmita Pathak and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.
For Scientific American, this is Kendra Pierre-Louis. Have a great week!
