An area of high pressure over the south-central U.S. produced unseasonable and, in some places, record-breaking warmth on September 15, 2026, as shown in this map of modeled air temperatures from GEOS (Goddard Earth Observing System).
NASA Earth Observatory/Michala Garrison
While the calendar indicated that astronomical summer was winding down, a swath of the south-central United States was sweltering under a heat dome in mid-September 2026.
This map shows air temperatures in the contiguous U.S. on September 15, 2026, at 4 p.m. Central Time (21:00 Universal Time), modeled at 2 meters (6.5 feet) above the ground. It was produced by combining satellite observations with temperatures predicted by a version of the GEOS (Goddard Earth Observing System) model, which uses mathematical equations to represent physical processes in the atmosphere. The darkest reds indicate areas where temperatures approached or exceeded 40 degrees Celsius (104 degrees Fahrenheit).
More than 41 million people in the U.S.—about 12 percent of the population—were under a National Weather Service extreme heat advisory, extreme heat watch, or extreme heat warning on September 15. The high temperatures spanned large portions of several states, such as Texas, Oklahoma, Arkansas, Missouri, and Tennessee. Meteorologists warned that high humidity, limited cloud cover, and light winds could make temperatures feel higher than thermometer readings and increase the risk of heat-related illnesses.
Several locations set new daily high temperature records on September 15. These included Dallas, Texas, at 101ºF (38ºC), Memphis, Tennessee, at 99ºF (37ºC), and Nashville, Tennessee, at 100ºF (38ºC). The cities were all at least 12ºF warmer than normal that day, with Nashville breaking its daily-high record from 1927. The day before, Nashville also set a record-high minimum temperature of 75ºF (24ºC).
A weather phenomenon meteorologists call a heat dome was responsible for driving temperatures up across the region. A heat dome develops when an area of high pressure in the upper atmosphere pushes hot air toward the surface and traps it there. Heat domes put the brakes on convection and suppress clouds and precipitation. This allows sunlight to reach Earth’s surface relatively unhindered and further elevate air temperatures.
The stretch of unseasonable temperatures follows the warmest June through August in the contiguous United States in a 132-year record, according to NOAA. The three-month period in 2026 was 0.4ºF warmer than the previous records, set in 1936 and 2021.
The curving, parallel mountain ridges of the Sierra Madre Oriental are an eye-catching feature of northeastern Mexico’s landscape. The spot where these folds nestle up against Mexico’s second-largest metropolitan area captured the attention of an astronaut aboard the International Space Station, who took this photo on August 26, 2026.
Monterrey, the capital of the state of Nuevo León, is an industrial hub supporting heavy industries such as ironworks and steelworks, as well as manufacturing facilities for goods ranging from textiles to processed foods to glass and plastics. The metropolitan area is home to 5.3 million people, according to the 2020 census. And while the city has seen overall population growth since 1990, the number of people living within 5 kilometers (3 miles) of the city center has declined, researchers have found—a trajectory shared with many of Mexico’s metropolitan areas.
In Monterrey’s case, urban expansion runs up against some unforgiving terrain. Along the city’s southern edge, layers of limestone, deposited in the late Mesozoic era and then folded between about 80 and 50 million years ago, form the Sierra Madre Oriental. Over millions of years, weaker rock layers have eroded away, leaving behind the distinct ridgelines that bound Monterrey today.
The Río Santa Catarina carves through the mountains and onto the semiarid floodplain where the city lies. Because of the dry environment, the river carries little to no water for much of the time. But its channel is crucial for collecting runoff from summer rains and serves as an important natural area for plant and animal life within the city.
The river runs through Monterrey’s urban core and between several island-like protrusions of folded rock. One of these is the Sierra Las Mitras, a state nature reserve established in 2000. The mountain ridge rises approximately 1,500 meters (4,900 feet) over the city and provides a haven for wildlife. As conditions become cooler and wetter with higher elevations, vegetation turns from cacti and thorny shrubs on lower rocky slopes to oak and pine forests higher on the ridge. Cerro de la Silla (Mount Silla or Saddle Hill) is another prominent feature of the landscape, contrasting with the built environment.
Near the city’s border with the Sierra Madre Oriental sits Universidad de Monterrey, a host venue for the NASA Space Apps Challenge. This annual hackathon will take place in November 2026 in person and virtually at sites around the world. Participating teams use NASA and partner agency data to tackle challenges in fields such as software development, astrophysics, space exploration, and agriculture.
Astronaut photograph ISS075-E-70481 was acquired on August 26, 2026, with a Nikon Z9 digital camera using a focal length of 400 millimeters. It is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA Johnson Space Center. The image was taken by a member of the Expedition 75 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Story by Lindsey Doermann.
Tropical Storm Arthur’s white storm clouds cover the waters off the U.S. Gulf Coast. Some clouds extend inland over parts of Texas and Louisiana.
NASA Earth Observatory/Michala Garrison
White and purple areas of cloud off the Gulf Coast indicate the cooler areas of cloud tops associated with Tropical Storm Arthur.
NASA Earth Observatory/Michala Garrison
Tropical Storm Arthur’s white storm clouds cover the waters off the U.S. Gulf Coast. Some clouds extend inland over parts of Texas and Louisiana.
NASA Earth Observatory/Michala Garrison
White and purple areas of cloud off the Gulf Coast indicate the cooler areas of cloud tops associated with Tropical Storm Arthur.
NASA Earth Observatory/Michala Garrison
Natural color
brightness temperature
Images from the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite show Tropical Storm Arthur on the morning of June 17, 2026. The left image is natural color; the right shows infrared signals known as brightness temperature. NASA Earth Observatory images by Michala Garrison.
Tropical Storm Arthur, the first named storm of the 2026 Atlantic hurricane season, brought high winds and heavy rain to the U.S. Gulf Coast in mid-June.
NASA’s Terra satellite captured this natural-color image (left) at 10:30 a.m. Central Time (15:30 Universal Time) on June 17. The second image (right) depicts infrared signals known as brightness temperature, which help distinguish cooler cloud tops (white and purple) from the warmer surface below (yellow and orange). Around the time these images were acquired, the system had just recently been designated a tropical storm, according to the National Hurricane Center (NHC).
Though Arthur stayed below hurricane strength, it still delivered strong winds to parts of the Gulf Coast as it tracked northeast. The storm had maximum sustained winds of 40 miles (65 kilometers) per hour around the time these images were captured. Tropical-storm-force winds extended 175 miles (280 kilometers) from the storm’s center, the NHC reported. Measurements at Galveston, Texas, for instance, showed a gust of 48 miles per hour.
The storm also produced heavy rainfall that the National Weather Service warned could lead to life-threatening flash flooding. Estimates from IMERG (the Integrated Multi-Satellite Retrievals for GPM), a product of the GPM (Global Precipitation Measurement) mission, showed high rainfall rates over Gulf waters and extending inland on June 17.
As Arthur weakened and became less organized, it continued to bring abundant moisture to central Gulf Coast states on June 18. The National Weather Service reported rainfall rates of 3 inches (7.6 centimeters) per hour in southeastern Louisiana. Forecasts indicated that storm-total rainfall amounts could exceed 12 inches (30 centimeters) in areas, with some locations seeing totals approaching 20 inches (51 centimeters).
NASA Earth Observatory images by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen.
The reservoir appears lake-like and expansive in an image acquired in June 2023.
NASA Earth Observatory/Michala Garrison
The reservoir is nearly empty by May 2026. The Gila River’s natural channel is now visible and flanked with green vegetation in what had been the bottom of the reservoir.
NASA Earth Observatory/Michala Garrison
The reservoir appears lake-like and expansive in an image acquired in June 2023.
NASA Earth Observatory/Michala Garrison
The reservoir is nearly empty by May 2026. The Gila River’s natural channel is now visible and flanked with green vegetation in what had been the bottom of the reservoir.
NASA Earth Observatory/Michala Garrison
June 7, 2023
May 22, 2026
Little water remains in the San Carlos Reservoir in May 2026 (right) compared to fuller conditions in June 2023 (left). Images were captured by the OLI (Operational Land Imager) on the Landsat 9 and 8 satellites, respectively. NASA Earth Observatory images by Michala Garrison.
The Gila River is among the Southwest’s most important rivers, delivering water for people, farms, and wildlife while linking the snow-fed mountains of southwestern New Mexico to the desert lowlands of southwestern Arizona.
In wetter years, seasonal snowfall on the Mogollon Mountains and Black Range provides much of the river’s spring flow and helps refill San Carlos Reservoir, which is formed by the Coolidge Dam. When filled to capacity, the reservoir is one of Arizona’s largest bodies of water.
However, in 2026, lackluster snowfall left the mountain snowpack in the Gila River watershed at 2 percent of the 1991-2020 March median. The limited snowpack pushed April streamflow to 39 percent of normal. By June, after mandatory water releases for downstream agriculture, the reservoir held less than 400 acre-feet of water.
The Landsat image above (right) shows the near-empty reservoir on May 22, 2026, when it stored 389 acre-feet of water—less than 1 percent full; the other image (left) shows the same area in June 2023, when it was about 60 percent full. The green vegetation growing along the river channel and reservoir edge includes a mixture of tamarisk, willow, cottonwood, sedges, and grasses.
Officials closed the reservoir indefinitely on June 5, 2026, after the declining water levels contributed to low oxygen levels—hypoxia—that killed virtually all of its fish. Species living in the reservoir included largemouth bass, black crappie, bluegill, channel catfish, flathead catfish, and several stocked species, including brown trout and rainbow trout. The decomposing fish may pose health risks to people attempting to boat or fish, the San Carlos Recreation and Wildlife Department warned.
The reservoir has hit similarly low water levels in the past, running out of water at least 20 times since it was filled in 1930, according to news reports. Even when the dam and reservoir were first dedicated, there was enough grass growing on the dried reservoir bottom that humorist Will Rogers famously quipped to President Calvin Coolidge: “If that was my lake, I’d mow it.”
Other years with major fish kills include 1976 and 2018. After more than 5 million fish died during a similar event in 1976, the Gila Heraldreported that it took five years for the lake’s ecosystem to rebound.
The region is currently in the midst of a multi-year dry period that has left much of the Gila River’s headwaters in New Mexico in a state of severe drought, according to data from the U.S. Drought Monitor.
However, the river’s flow is highly variable, and heavy rains during the coming wet season could help the reservoir recover. A seasonal monsoon outlook released by NOAA in May 2026 projected a 33 to 50 percent chance that an above-average amount of rain would fall in the region that summer. El Niño in the central and eastern equatorial Pacific, which was strengthening in late spring 2026, can make heavy rains in the U.S. Southwest more likely.
NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey.Story by Adam Voiland.
TEMPO detected high concentrations of nitrogen dioxide during the morning commute at 7:05 a.m. local time on May 18, 2026 (left), along the New York-Washington corridor. The instrument detected lower levels of the gas at 3:05 p.m. (right), after chemical reactions involving nitrogen dioxide had contributed to elevated ozone concentrations in the afternoon.
NASA Earth Observatory/Michala Garrison
TEMPO detected high concentrations of nitrogen dioxide during the morning commute at 7:05 a.m. local time on May 18, 2026 (left), along the New York-Washington corridor. The instrument detected lower levels of the gas at 3:05 p.m. (right), after chemical reactions involving nitrogen dioxide had contributed to elevated ozone concentrations in the afternoon.
NASA Earth Observatory/Michala Garrison
TEMPO detected high concentrations of nitrogen dioxide during the morning commute at 7:05 a.m. local time on May 18, 2026 (left), along the New York-Washington corridor. The instrument detected lower levels of the gas at 3:05 p.m. (right), after chemical reactions involving nitrogen dioxide had contributed to elevated ozone concentrations in the afternoon.
NASA Earth Observatory/Michala Garrison
TEMPO detected high concentrations of nitrogen dioxide during the morning commute at 7:05 a.m. local time on May 18, 2026 (left), along the New York-Washington corridor. The instrument detected lower levels of the gas at 3:05 p.m. (right), after chemical reactions involving nitrogen dioxide had contributed to elevated ozone concentrations in the afternoon.
NASA Earth Observatory/Michala Garrison
7:05 am
3:05 pm
TEMPO detected high concentrations of nitrogen dioxide during the morning commute at 7:05 a.m. local time on May 18, 2026 (left), along the New York-Washington corridor.The instrument detected lower levels of the gas at 3:05 p.m. EDT (right), after chemical reactions involving nitrogen dioxide had contributed to elevated ozone concentrations in the afternoon. NASA Earth Observatory images by Michala Garrison.
More than 35 million people live along the New York–Washington corridor and breathe the region’s air. While air quality has improved significantly in recent decades, outbreaks of ground-level ozone remain common, particularly in the warm summer months, when the chemical reactions that produce the pollutant accelerate and stagnant air allows ozone to accumulate.
A reminder of this seasonal phenomenon came earlier than usual in 2026, when a mid-May heat wave prompted the New York State Department of Health and the New York Department of Environmental Conservation to issue a health advisory on May 17 over concerns about ozone. The code orange advisory warned young people, older adults, and those working or exercising outdoors to limit activity due to ozone’s respiratory and cardiovascular health impacts.
As expected, ground-based air-quality sensors operated by state and federal agencies showed ozone reaching unhealthy levels for sensitive groups on May 18, something that typically happens several times per year. Meanwhile, NASA’s TEMPO (Tropospheric Emissions: Monitoring of Pollution) instrument observed the event from geostationary orbit 22,000 miles (35,000 kilometers) above the equator, a unique vantage point that allows the sensor to collect frequent observations of air pollution.
TEMPO detects nitrogen dioxide (NO2), a gas emitted by burning fuels, particularly by motor vehicles, that contributes to ozone formation. “There’s often a clear and interesting pattern in TEMPO’s nitrogen dioxide data during ozone alert days,” said Hazem Mahmoud, an atmospheric scientist at NASA’s Atmospheric Science Data Center at Langley Research Center. “We see high concentrations of nitrogen dioxide during the early morning commute that drop off sharply in the late afternoon as ozone increases.”
The decline occurs as sunlight fuels photochemical reactions involving nitrogen dioxide, volatile organic compounds, and oxygen that lead to ozone formation. By late afternoon, these reactions deplete much of the available nitrogen dioxide, slowing ozone production until the cycle begins again the next day.
The pair of images above underscores the pattern. The image on the left was acquired at 7:05 a.m. local time when nitrogen dioxide concentrations were high during the morning commute. By 3:05 p.m. (right), most of the nitrogen dioxide had declined substantially, and surface ozone levels were elevated (below). Meanwhile, afternoon sea breezes appear to have transported the remaining nitrogen dioxide slightly to the west. Note that the data shown is provisional, and processing methods are still being refined.
Sensors on earlier polar-orbiting satellites, such as OMI (Ozone Monitoring Instrument) and TROPOMI (Tropospheric Monitoring Instrument), sampled nitrogen dioxide over New York once per day. After its launch in 2023, TEMPO began providing data every hour, allowing researchers to track the evolution and dispersion of air pollution at much finer time scales.
“TEMPO is helping fill data gaps between ground stations and allowing us to ask new questions,” Mahmoud said. The mission provides data that can improve not only air quality forecasts during crisis situations, such as wildfires, but also the atmospheric models used to forecast the daily rhythms of urban pollution. Such models help researchers understand how natural factors such as winds, humidity levels, and air temperatures influence pollution plumes over the course of a day.
TEMPO detected elevated ozone concentrations in an area extending from New York City to Washington, D.C., at 5:05 p.m. on May 18, 2026.
NASA Earth Observatory/Michala Garrison
TEMPO also detects ozone directly, but determining how much of that ozone is near the surface versus higher in the atmosphere can be challenging. Most of Earth’s ozone resides in the stratosphere, well above the troposphere, where people live and breathe. At times, however, stratospheric ozone can be transported downward into the troposphere. During events known as stratospheric intrusions, it can even descend far enough to affect air quality at the surface and add to the ozone produced at ground level.
By combining TEMPO observations with other sources of information, researchers are studying the processes that influence the distribution of ozone vertically in the atmosphere. On May 18, NASA’s ground-based tropospheric lidar network (TOLNet) in New York City recorded high concentrations of ozone near the surface, indicating that TEMPO was detecting mostly surface-level ozone associated with urban emissions and not ozone aloft, said Mahmoud.
However, on May 19, the same sensor observed a layer of ozone descending from above 5 kilometers (3 miles), he added, a clue that some of the ozone TEMPO detected that day may have originated in the stratosphere. “This is the type of information that leads to better air quality forecast models and more accurate alerts,” Mahmoud said. “Alerts can affect tens of millions of people and lead to disruptions in school, sports, and other activities, so it’s essential that they be as accurate as possible.”
On June 6, New York authorities issued another health advisory for ozone. People interested in following the event can access daily near-real-time TEMPO observations of ozone, nitrogen dioxide, and other gases on NASA’s Worldview browser, on an interactive Harvard & Smithsonian Center for Astrophysics browsing tool, and on NASA’s Earthdata portal.
NASA Earth Observatory images by Michala Garrison, using TEMPO data from NASA Earthdata.Story by Adam Voiland.
The Southern Patagonian Icefield is the largest expanse of ice in the Southern Hemisphere outside of Antarctica. The mass of glacial ice extends hundreds of kilometers along the spine of the Andes, feeding dozens of dynamic outlet glaciers that grind their way down from higher elevations. Many of these rivers of ice terminate in the sea or in proglacial lakes.
An astronaut aboard the International Space Station photographed one of these glaciers—Tyndall Glacier in southern Chile—through a layer of ethereal clouds on May 10, 2026. Fragments of ice that had calved off its terminus were visible floating on Lago Geikie.
Like most Patagonian glaciers, Tyndall has been shrinking since the end of the Little Ice Age about 150 years ago. Lago Geikie formed at Tyndall’s terminus around 1940, according to glaciologist Mauri Pelto of Nichols College, and gradually expanded as the ice retreated. Part of the glacier previously terminated in Lago Tyndall to the east, but thinning ice cut off that outlet by 2010, Pelto said. (The ice’s retreat also exposed bedrock along its eastern edge that contains scores of ichthyosaur fossils.)
Along with thinning, ice calving off the glacier’s front has reduced its volume. Tyndall has lost 2.2 kilometers (1.4 miles) in length since November 2022, Pelto said, following about a decade of limited retreat with considerable thinning. A significant calving event in March and April 2023 contributed to the recent uptick in ice retreat. During that time, satellites observed several large icebergs breaking away from Tyndall’s terminus.
Austral autumn in 2026 was a time of active calving retreat at Tyndall (and some neighboring glaciers), Pelto said, albeit more incremental than three years prior. “The substantial crevasses crisscrossing the glacier near the calving front lead to many smaller icebergs,” he said. On the other hand, larger tabular icebergs tend to form when there are fewer deep crevasses near the terminus and the glacier’s ice is thinner.
May 10, 2026
The ice cliff at the terminus casts a substantial shadow, which can help scientists estimate the height of the glacier’s front. Pelto’s calculations, using information about the Sun’s position provided with the image, indicate that Tyndall’s front loomed 30–40 meters (100–130 feet) above the lake surface in May 2026. Observations from orbit, including astronaut photographs, can help scientists monitor and understand glaciers in remote regions where ground-based observations are scarce.
As for what comes next for Tyndall, Pelto expects many more small icebergs to continue breaking off, given the heavily crevassed appearance of the calving front. “Look for a burst of iceberg production next fall.”
Astronaut photograph ISS074-E-582898 was acquired on May 10, 2026, with a Nikon Z9 digital camera using a focal length of 560 millimeters. It is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA Johnson Space Center. The image was taken by a member of the Expedition 74 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Story by Lindsey Doermann.
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