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CBS News
7 days ago
- Climate
- CBS News
Maps show U.S. heat advisories, high temperatures as heat dome moves east
The extreme heat that has baked much of the central United States this week is slowly shifting east ahead of the weekend, forecasters said. More than 130 million Americans across at least 20 states are under heat alerts on Thursday. Parts of the Midwest, including the Corn Belt, have felt the high temperatures for multiple days. Temperatures on Thursday are forecast to be 10 to 15 degrees above average for this time of year with feels-like temperatures over 100 degrees expected in multiple areas. Some parts of the Mississippi Valley will continue to see high temperatures over 90 degrees for a few more days, even as the heat dome moves over parts of the Northeast. A heat dome happens when hot air is trapped over an area due to a persistent high pressure system, William Gallus, a professor of atmospheric science at Iowa State University, said. Heat domes can last for days to weeks and can stretch over multiple states. With extreme heat in the Corn Belt, a region including parts of the Plains and Central Mississippi Valley, a phenomenon known as corn sweat has made the humidity worse, experts said. "There are pores on the bottom side of the leaves," Iowa state climatologist Justin Glisan told CBS News national correspondent Lana Zak. "And that's where oxygen is released, but also water vapor." The process can add up to 10 degrees to the feels-like temperature, Glisan said, because just 1 acre of corn can release as much as 4,000 gallons of water into the air per day. Iowa has around 13 million acres of corn.
Axios
22-07-2025
- Climate
- Axios
A heat dome and "corn sweat" are driving this week's dangerous heat wave
A heat dome — plus the "corn sweat" phenomenon in some areas — is bringing dangerous levels of heat and humidity to much of the country east of the Rockies this week. Why it matters: Heat warnings and advisories stretch from Louisiana and the Florida panhandle up to Chicago and beyond as of Tuesday afternoon, covering nearly 85 million Americans. Driving the news: The main driver is hot, moist air being drawn up from the Atlantic and trapped by a high pressure ridge. Also contributing in some places: "Corn sweat," wherein vast amounts of growing corn and other produce give off moisture through evapotranspiration, further increasing humidity levels in and around agricultural zones. "While corn sweat is never the main reason for major heat," Axios Des Moines' Linh Ta wrote back in 2023, "it can add to it." What they're saying: " This is the time of the year when humidity contributions from corn sweat are highest — around the time of tasseling and pollination, when the flower emerges from the corn stalk," as Iowa state climatologist Justin Glisan told the Washington Post. Zoom in: Conditions could be particularly brutal in Chicago, where the local National Weather Service office is warning of heat indices over 105°F for Wednesday and Thursday. High humidity is especially dangerous, as Axios' Tina Reed and Natalie Daher recently reported, disrupting our bodies' ability to regulate temperatures. Threat level: Long-duration heat waves can be particularly serious events, with warm evenings offering less of a reprieve and extreme heat having a cumulative effect on our health. Extreme heat is the most deadly weather event in the U.S., and research has shown that human-driven climate change is making such events both more intense and more frequent. What they're saying: " Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors," the NWS Milwaukee office advises.
USA Today
21-07-2025
- Climate
- USA Today
'Corn sweat' will add to punishing heat, humidity in Midwest this week.
The process is officially known as evapotranspiration, which is how plants, including corn, release water vapor into the atmosphere. It's high summer in the Midwest and the corn is "sweating." The process, which despite its nickname does not involve any actual sweating in our sense of the word, is officially known as evapotranspiration, which is how plants, including corn, release water vapor into the atmosphere, according to a statement from Taranis, a crop intelligence firm. Here's how it works: Commonly called "corn sweat," water evaporating from plants enters the atmosphere, combines with other water molecules and humidifies the air. In the Plains and Midwest regions, where there are millions of acres of corn and soybean crops, this can worsen stifling heat by driving up the humidity levels, making hot summer days all the more miserable. "What we're talking about is evapotranspiration, which occurs with all vegetation," Iowa state climatologist Justin Glisan said in an e-mail to USA TODAY. How much does corn 'sweat'? During the growing season, an acre of corn "sweats off" about 3,000 to 4,000 gallons of water a day, according to the U.S. Geological Survey. In Iowa, corn pumps out "a staggering 49 to 56 billion gallons of water into the atmosphere each day" throughout the state, the National Weather Service said. That can add 5 to 10 degrees to the dew point, a measure of the humidity in the air, on a hot summer day. In states such as Illinois, which boasts about 12 million acres of corn, that adds up to 48 billion gallons of water daily – enough to fill 73,000 Olympic-size swimming pools, according to Taranis. Weather patterns still rule However, Glisan said weather patterns contribute more to the heat and humidity in the Midwest than does corn sweat, which he said is "a more local or smaller scale effect." "Corn transpiration is an important moisture contributor, though not the dominant factor," he said to USA TODAY. He said larger-scale (think state to regional scale) weather patterns provide much more low-level moisture via southerly and westerly advection – moisture from the Gulf or through the lower-levels of the atmosphere from the Pacific, for example. "With the large heat dome setting up over the Midwest this coming week, southerly moist flow will increase surface dew points and in the presence of unseasonably hot air temperatures, produce oppressive heat index values," Glisan said. How hot will temperatures get this week? How hot? The weather service in Chicago is warning that the heat index in Illinois could reach 115 degrees by Wednesday and Thursday, July 23-24. Elsewhere, parts of Texas, Arkansas and Louisiana will have highs peak at near or above 100 degrees, and a much larger area of the South, Midwest and Great Lakes will see a heat index surpassing 100 degrees, meteorologist Jonathan Erdman said. Corn sweat will only add to the misery in the Midwest, Glisan said: "Of course, there's a local contribution from corn/bean transpiration which can add additional low-level moisture and exacerbate dew points." Does corn sweat have any benefits? While corn sweat might make summer days feel more oppressive, it's actually a sign of healthy, growing crops, Taranis reported. "The process of evapotranspiration is essential for plant growth, helping crops reach their full potential." Contributing: Christopher Cann, John Bacon, USA TODAY
Yahoo
03-07-2025
- Climate
- Yahoo
Drought monitor map shows an increase in dry conditions across Iowa. Why?
With the summer kicking off and temperatures rising, will Iowa's drought conditions remain steady or will a drop in rainfall lead to worsening conditions? The U.S. Drought Monitor's weekly map tracks the progress as drought retreats from large portions of Iowa. The newest Drought Monitor report, released on June 5, showed 28% of Iowa with no dryness or drought. That's worse than the last report on May 29, when 44% of Iowa reported no abnormal dryness or drought. The portion of the state in moderate drought also increased to 13% compared to 9% the week prior. Moderate drought conditions are concentrated in northwestern, northeastern and southern counties. Current conditions are worse than this time last year, when for a brief period, none of the state was under moderate drought conditions. All of Polk County is now in abnormally dry conditions, according to the Drought Monitor. In the prior report, only 0.1% was abnormally dry. Drought conditions could worsen if weather patterns play out as expected over the next few months in Iowa. Iowa's long-range forecast has signs that the state could see an elevated warm and dry period, said Justin Glisan, the state's climatologist. "That doesn't mean that we're not going to see rainfall," he said. "It's just looking like the potential is there for less than what we would expect in summertime." Iowa isn't getting as many storm systems coming through as we had last spring through summer, either, Glisan said. Iowa's rainfall is mostly thunderstorm-produced, which can vary in timing. Iowa drought conditions: Des Moines metro residents asked to cut back on lawn watering The U.S. Drought Monitor offers a state-by-state tracking of drought conditions across the country. New maps and forecasts are released each Thursday. The intensity levels range from abnormally dry, or D0, to exceptional drought, or D4. Typically under D0 conditions, corn can show drought stress. Pond levels start to decline under moderate drought conditions and soybeans abort pods, according to the Drought Monitor. The Drought Monitor also has a look-back chart that compares drought conditions from 3 months ago up to one year ago. Glisan also noted that Iowans can submit their own dryness observations to him at the Iowa Climatology Bureau, the National Weather Service or the U.S. Drought Monitor. Victoria Reyna-Rodriguez is a general assignment reporter for the Register. Reach her at vreynarodriguez@ or follow her on Twitter @VictoriaReynaR. This article originally appeared on Des Moines Register: Iowa Drought Monitor: Will warm weather increase drought?
Yahoo
23-06-2025
- Climate
- Yahoo
Iowa corn beginning to silk, soybeans blooming ahead of normal
Corn growing near West Des Moines on June 22, 2025. (Photo by Cami Koons/Iowa Capital Dispatch) Across the state of Iowa, approximately 2% of planted corn acres are beginning to silk, and 13% of soybean acres are blooming, which is five days ahead of the five-year average, according to the crop progress and condition report. The report, put out weekly by the U.S. Department of Agriculture's National Agricultural Statistics Service, showed Iowa corn rated 83% good to excellent and soybeans rated 77% good to excellent. Iowa's oat crop also rated highly with 85% good or excellent. Nearly all oats in the state, 81%, have headed and 27% are coloring. The first cutting of alfalfa hay was nearly completed during the reporting period from June 16 through June 22. Twenty-four percent of the second cutting is complete. SUBSCRIBE: GET THE MORNING HEADLINES DELIVERED TO YOUR INBOX The state had an average precipitation of 1.82 inches during the reporting period, which was about six-tenths of an inch above the normal. Some areas of the state had higher precipitation for the reporting period, like Mason City which accumulated 4.41 inches — the most for the week. Soil moisture conditions improved slightly from last week, on average 73% of topsoil moisture was adequate, and just 16% of topsoil was short of moisture. Subsoil moisture for the state as a whole rated 65% adequate and 21% short. Soil moisture conditions were the worst in southern regions, in particular the southwest region, and also rated poorly in northwest and west central portions of the state. Temperatures across Iowa were high during the reporting period, with an average of 76 degrees Fahrenheit, which is nearly 5 degrees above normal, according to State Climatologist Justin Glisan. 'Exceedingly warm daytime temperatures in concert with high dewpoints and sustained strong southerly winds produced anomalous conditions not seen at many locations in the observational record,' Glisan wrote in the preliminary weather summary for the state. Iowa Secretary of Agriculture Mike Naig said the hot, humid and windy conditions from the past week 'really made it feel like summer.' 'Some areas across north-central Iowa received several inches of rain with other locations receiving uninvited hail and high winds,' Naig said. 'The warmer temperatures and increased chances for rain are likely to continue through the end of the month.' SUPPORT: YOU MAKE OUR WORK POSSIBLE
