Science
We Mapped Heat in 3 U.S. Cities. Some Sidewalks Were Over 130 Degrees.
We usually talk about summertime heat in terms of how hot the air is, but there’s another metric that matters: the temperatures of roads, sidewalks, buildings, parking lots and other outdoor surfaces. Hot surfaces can make the places people live and work more dangerous, and can increase the risk of contact burns.
Just consider this image, captured recently by satellite, of surface temperatures across Phoenix.
Sources: U.S.G.S. Landsat via Google Earth Engine; U.S. Census.
Note: Satellite image taken at 12:03 p.m. local time. Higher-uncertainty pixels removed.
Around noon on July 10, huge parts of the nation’s fastest-growing large city were 120 degrees Fahrenheit, about 49 Celsius, or hotter to the touch. Had you been unlucky or unwise enough to actually touch it with bare skin, it could have caused injury within minutes.
On the city’s desert fringes, in territory governed by Native American nations, the land was even hotter, 150 degrees or more.
So far this summer, the Arizona Burn Center, which serves Phoenix and the broader Southwest, has admitted 65 people for severe heat-related burns, according to Dr. Kevin Foster, the center’s director. Six of these people died from their injuries. Last summer, the center recorded 14 such deaths.
Yet even that figure is small compared with the 645 heat-related deaths that were identified last year in Maricopa County, which includes Phoenix. That was the highest number on record for the county. (This year, the county has so far reported 23 heat-related deaths and is investigating 322 more.)
Surface temperatures are just one of many factors that cities are thinking about as they try to protect residents from extreme heat, said Ladd Keith, an associate professor in the School of Landscape Architecture and Planning at the University of Arizona.
In an environment as complex as a city, heat can harm people, pets and wildlife in many different settings and circumstances, Dr. Keith said. For officials, it can be tricky to figure out which exact combination of policies and actions might prove most beneficial to public health.
Phoenix, for instance, is trying to plant more trees and increase shade. The city’s “Cool Pavement” program has treated 120 miles of asphalt to help it reflect more sunlight and stay cooler as a result. But from a cost-benefit perspective, might it make more sense to put those resources toward building more heat-tolerant homes or addressing homelessness instead? “It’s really hard to know what that mix is,” Dr. Keith said.
What’s clear, he said, is the need to figure it out quickly. “Heat deaths are climbing faster than any of our investments to prevent them,” he said. And human-caused global warming keeps increasing the frequency and intensity of dangerous heat waves. “We’re chasing a moving target very slowly,” he said.
Sources: U.S.G.S. Landsat via Google Earth Engine; U.S. Census.
Note: Satellite image taken at 11:45 a.m. local time. Higher-uncertainty pixels removed.
Sacramento is known, with pride, as the City of Trees. But tree cover isn’t distributed equally there, and neither is exposure to broiling heat. On the northern and southern sides of California’s capital, residents of low-income neighborhoods have long contended with a shortage of shade and green space on sweltering days like last week’s.
Victoria Vasquez is the grants and public policy manager for California ReLeaf, a coalition of nonprofit groups that protect and grow the state’s urban forests. Funding for such work is always tight, Ms. Vasquez said. That hasn’t changed very much even as the West suffers through more and more record temperatures. “I wish that it did,” she said.
Still, she sees signs of movement in the right direction. Sacramento is considering a plan to increase citywide tree cover to 35 percent from 19 percent by 2045. Under the Inflation Reduction Act, the United States Forest Service received $1.5 billion to support urban forest programs.
When neighborhood associations see how quickly they can reap the benefits of planting and maintaining trees, Ms. Vasquez said, “that is an infectious, positive change.”
Sources: U.S.G.S. Landsat via Google Earth Engine; U.S. Census.
Note: Satellite image taken at 11:55 a.m. local time. Higher-uncertainty pixels removed.
In Portland, Ore., tree-filled areas like Forest Park, on the city’s west side, provided oases of cool last week. Yet Vivek Shandas, a professor of urban planning at Portland State University, and his colleagues recently discovered that the city’s overall tree cover decreased somewhat between 2014 and 2020. One likely culprit? Trees are often removed when houses are sold and residential areas redeveloped.
The medical examiner’s office in Multnomah County, which includes Portland, said last week that it was investigating five deaths for links to the recent blistering heat.
In many ways, Portland has become much more attuned to heat threats ever since a heat dome killed hundreds of people in Oregon and Washington in the summer of 2021, Dr. Shandas said. The city is communicating the risks more actively. It has provided portable cooling units to low-income residents. Still missing, Dr. Shandas said, are the changes to building codes and construction practices that would truly ready Portland for the hotter years and decades to come.
“The things that are low-hanging fruit right now, I think have pretty much been picked,” he said. “The longer-term, sustained, deep retrofit that the city needs in order to be prepared for the increasing intensity and frequency of these heat waves? I have yet to see any of that.”
Our universe might be chock-full of cosmic wonder, but you can observe only a fraction of astronomical phenomena with the naked eye. Meteor showers, natural fireworks that streak brightly across the night sky, are one of them.
The latest observable meteor shower will be the Lyrids, which has been active since April 14 and is forecast to continue through April 30. The shower reaches its peak April 21 to 22, or Tuesday night into Wednesday morning.
According to NASA, the Lyrids are one of the oldest known meteor showers, and have been enjoyed by stargazers for nearly 3,000 years. Their bright, speedy streaks are caused by the dusty debris from a comet named Thatcher. They appear to spring from the constellation Lyra, which right now can be seen in the eastern sky at night in the Northern Hemisphere.
The moon will be about 27 percent full tonight, appearing as a thick crescent in the sky, according to the American Meteor Society.
To get a hint at when to best watch for the Lyrids, you can use this tool, which relies on data from the Global Meteor Network. It shows fireball activity levels in real time.
And while you gaze at the heavens, keep an eye out for other stray meteors streaking across the night sky. Skywatchers are reporting that the amount of fireballs is double what is usually seen by this point in the year.
Where meteor showers come from
There is a chance you might see a meteor on any given night, but you are most likely to catch one during a shower. Meteor showers are caused by Earth passing through the rubble trailing a comet or asteroid as it swings around the sun. This debris, which can be as small as a grain of sand, leaves behind a glowing stream of light as it burns up in Earth’s atmosphere.
Meteor showers occur around the same time every year and can last for days or weeks. But there is only a small window when each shower is at its peak, which happens when Earth reaches the densest part of the cosmic debris. The peak is the best time to look for a shower. From our point of view on Earth, the meteors will appear to come from the same point in the sky.
The Perseid meteor shower, for example, peaks in mid-August from the constellation Perseus. The Geminids, which occur every December, radiate from the constellation Gemini.
How to watch a meteor shower
Michelle Nichols, the director of public observing at the Adler Planetarium in Chicago, recommends forgoing the use of telescopes or binoculars while watching a meteor shower.
“You just need your eyes and, ideally, a dark sky,” she said.
That’s because meteors can shoot across large swaths of the sky, so observing equipment can limit your field of view.
Some showers are strong enough to produce up to 100 streaks an hour, according to the American Meteor Society, though you probably won’t see that many.
“Almost everybody is under a light-polluted sky,” Ms. Nichols said. “You may think you’re under a dark sky, but in reality, even in a small town, you can have bright lights nearby.”
Planetariums, local astronomy clubs or even maps like this one can help you figure out where to go to escape excessive light. The best conditions for catching a meteor shower are a clear sky with no moon or cloud cover, sometime between midnight and sunrise. (Moonlight affects visibility in the same way as light pollution, washing out fainter sources of light in the sky.) Make sure to give your eyes at least 30 minutes to adjust to seeing in the dark.
Ms. Nichols also recommends wearing layers, even during the summer. “You’re going to be sitting there for quite a while, watching,” she said. “It’s going to get chilly, even in August.”
Bring a cup of cocoa or tea for even more warmth. Then lie back, scan the sky and enjoy the show.
Where weather is least likely to affect your view
Storm systems sweep across the country in early spring, and some will be obscuring skies tonight. But there will still be plenty of areas with clear skies, particularly in parts of the central United States.
“The best spot is going to be in the Upper Midwest,” said Rich Bann, a meteorologist with the Weather Prediction Center.
Minnesota, Wisconsin and Iowa will offer especially good sky-viewing weather and a beach on the Great Lakes could be a nice spot to look up at the stars.
But don’t expect to view the show from Chicago, as Illinois could see some thunderstorms. The weather will be better in the Northern and Central Plains, particularly the eastern Dakotas.
High, wispy clouds are expected over the Ohio and Tennessee Valleys and into parts of the Mid-Atlantic. But, Mr. Bann said, “you may be able to see some shooting stars through thin clouds.”
Clouds will be draped across much of the Southeast and the Northeast, though there could be some clearing in Florida, Georgia, the Carolinas and Virginia. Remember, the meteors could be visible all night long. If you look outside and see clouds, try again later.
Catching the spectacle will be challenging across much of the West, particularly from Washington into Northern California, where a storm system is bringing rain and snow. That system will move east overnight.
There are likely to be some pockets of clear skies at times across southern Nevada, northwest Arizona and southwest Utah, Mr. Bann said.
Amy Graff contributed reporting.
WASHINGTON — Amid growing national security concerns, the FBI said Tuesday that it has launched a broad investigation in the deaths or disappearances of at least 10 scientists and staff connected to highly sensitive research, including four from the Los Angeles area.
“The FBI is spearheading the effort to look for connections into the missing and deceased scientists. We are working with the Department of Energy, Department of War, and with our state and state and local law enforcement partners to find answers,” the agency said in a statement.
The FBI’s announcement comes after the House Oversight Committee announced that it would investigate reports of the disappearance and deaths of the scientists, sending letters seeking information from the agencies involved in the federal inquiry as well as NASA, which owns the Jet Propulsion Laboratory in La Cañada Flintridge, where three of the missing or dead scientists worked.
“If the reports are accurate, these deaths and disappearances may represent a grave threat to U.S. national security and to U.S. personnel with access to scientific secrets,” Reps. James Comer (R-Ky.), chairman of the committee, and Eric Burlison (R-Mo.) wrote in the letters.
President Trump told reporters last week that he had been briefed on the missing and dead scientists, which he described as “pretty serious stuff.” He said at the time that he expected answers on whether the deaths were connected “in the next week and a half.”
Michael David Hicks, who studied comets and asteroids at JPL, was the first of the scientists who disappeared or died. He died on July 30, 2023, at the age of 59. No cause of death was disclosed.
A year later, JPL physicist Frank Maiwald died at 61, with no cause of death disclosed.
Two other Los Angeles scientists are part of the string of deaths and disappearances.
On June 22, 2025, Monica Jacinto Reza, a materials scientist at JPL, disappeared while on a hike near Mt. Waterman in the San Gabriel Mountains.
On Feb. 16, Caltech astrophysicist Carl Grillmair was fatally shot on the porch of his Llano home. The Los Angeles County Sheriff’s department arrested Freddy Snyder, 29, in connection with the shooting. Snyder had been arrested in December on suspicion of trespassing on Grillmair’s property.
Snyder has been charged with murder.
There is no evidence at this point that the deaths and disappearances, which occurred over a span of four years, are connected.
A spokesperson for NASA, which owns JPL, said in a statement on X that the agency is “coordinating and cooperating with the relevant agencies in relation to the missing scientists.
“At this time, nothing related to NASA indicates a national security threat,” agency spokesperson Bethany Stevens wrote. “The agency is committed to transparency and will provide more information as able.”
Representatives from Caltech, which manages JPL, did not immediately respond to a request for comment.
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
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