The flow of the Mississippi River has slowed -- at times rivaling 40-year-lows -- allowing saltwater from the Gulf of Mexico to seep far up the river channel, threatening community water supplies at the river mouth.
In Iowa, about 58,000 fish died along a 42-mile stretch of the Des Moines River, according to state officials, and the cause of death appeared to be heat. Biologists measured the water at 97 degrees in multiple spots.
Across Indiana, wells have run dry, and farther across the nation's middle, many communities have invoked water restrictions to protect shrinking supplies.
"I've never seen anything quite like it," Justin Pedretti, who owns a farm near the boat ramp in Bonaparte, Iowa, and first reported the fish kill.
In 1895, the first year of such records for the nation, the average July temperature in the contiguous states was 72.1 degrees.
Since then, average temperatures have been rising, if slowly, according to U.S. records, climbing at the rate of 1.24 degrees per century.
This year, average temperatures spiked to 77.6 -- even above the long-term trends, the National Oceanic and Atmospheric Administration reported last week.
At the same time that temperatures have spiked, setting records in places as far-flung as Lansing and Greenville, S.C., the country has been hit with a spreading drought.
In early August, 62 percent of the contiguous United States was under moderate to exceptional drought, according to the U.S. Drought Monitor.
The heat and drought feed on each other, worsening conditions, scientists said. When the ground is wet, the water absorbs the sun's heat and expends it in evaporation; when the earth is dry in a drought, the ground simply warms.
The rising temperatures and spreading drought this year are consistent with what can be expected with the warming of the climate, said Jake Crouch, a climate scientist with NOAA.
"Any given year in the future could be above or below that rising trend," he said. "But if the current trend continues, the chances of years like this become greater."
The Midwest is particularly vulnerable to large swings, according to federal scientists, in part because it is farther from the oceans, which help to moderate temperatures.
"There is a high degree of confidence in projections that future temperature increases will be greatest in the Arctic and in the middle of continents," according to the U.S. Global Change Research Program. More