Nationwide
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Active weather prevailed across much of the South, East, and Midwest, as well as parts of the Plains, into the middle of July, followed by a southward shift in widespread shower activity. Meanwhile, a robust monsoon circulation provided limited Southwestern drought relief, particularly in parts of Arizona, New Mexico, and southwestern Colorado.
Farther north and west, however, little or no rain fell in California, the Great Basin, and the Northwest, where dozens of wildfires were in various stages of containment. Smoke and other particulate matter from those fires carried downwind at various atmospheric levels, producing hazy skies and reducing air quality—in some cases thousands of miles from the points of origin. Dry weather extended eastward across the nation’s northern tier as far east as Lake Superior. At the same time, heavy rain eased or eradicated drought in the remainder of the Great Lakes region, along with the Northeast.
In the driest areas of the northern and western United States, drought’s impact on water supplies, as well as rangeland, pastures, and a variety of crops, was further amplified by ongoing heat. Weekly temperatures averaged as much as 10°F above normal from the interior Northwest to the northern High Plains.
On July 19, temperatures as high as 110°F were reported in eastern Montana. Another pocket of hot weather was centered over the middle Atlantic States. In contrast, near- or slightly below-normal temperatures dominated the Plains, Midwest, and South.
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The West
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Showers associated with the Southwestern monsoon circulation provided limited drought relief in Arizona, New Mexico, and southwestern Colorado, while drought generally worsened across the northern Rockies and interior Northwest.
The Western drought continued to act on multiple time scales, ranging from a few weeks (mostly agricultural impacts) to two decades (ecological and hydrological effects). Dozens of wildfires, primarily across northern California and the Northwest, continued to burn through hundreds of thousands of acres of timber, brush, and grass, aided by hot, dry conditions, dry soils, and ample fuels. Wildfire smoke continued to degrade air quality in many areas of the country, well outside the West. In southern Oregon, the nation’s largest active wildfire—the lightning-sparked Bootleg Fire—has consumed more than 394,000 acres of vegetation and has destroyed at least 184 structures.
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Meanwhile, Washington led the country in several drought-related agricultural categories, according to the U.S. Department of Agriculture. On July 18, Washington’s topsoil moisture was rated 98 percent very short to short—highest on record since the beginning of the 21st century. Prior to this year, the Washington state record of 89 percent, very short to short, had been set on September 10, 2017. Washington also led the country on July 18 in very poor to poor ratings for rangeland and pastures (96 percent), spring wheat (88 percent), and barley (63 percent).
In addition to Washington, at least one-half of the rangeland and pastures were rated very poor to poor on that date in Montana (89 percent), Arizona (88 percent), Oregon (74 percent), Utah (72 percent), Nevada (65 percent), and Wyoming (52 percent). Partly due to the stunning drought-related impacts on agriculture, extreme to exceptional drought (D3 to D4) was broadly expanded across eastern Washington and environs, as well as parts of Montana and neighboring states. Moving to longer-term impacts, some of the West’s largest reservoirs and lakes continued to exhibit startling declines.
On the Colorado River behind Hoover Dam, the surface elevation of Lake Mead fell 135 feet in the 21-year period from July 1, 2000, to July 1, 2021, from 1,204 to 1,069 feet above sea level. By July 20, Lake Mead’s elevation stood at 1067.79 feet. Prior to the 21st century, Lake Mead’s surface elevation briefly fell below 1,100 feet only during two drought periods: 1955-57 and 1964-65. Since March 2014, the lake’s end-of-month surface elevation has been continuously below 1,100 feet—and currently stands at a record low since impoundment occurred more than 80 years ago.
Farther upstream, water is being released from Flaming Gorge Reservoir in Wyoming and Utah to boost the level of Lake Powell for the purpose of guarding hydropower generating capability. Elsewhere in Utah, the surface elevation of the Great Salt Lake fell to 4,191.4 feet on July 20, tying the previous record low set in 1963.
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In California, 154 primary intrastate reservoirs gained just 1.7 million acre-feet of water during the 2021 melt season, barely 20 percent of the historical recharge average of 7.9 million acre-feet. At the end of June, the 154 reservoirs held just 62 percent of their typical volume for this time of year—and had lost 16.6 million acre-feet of water (49 percent of the original volume) over the last two years. Current California storage (17.5 million acre-feet) is less than 5.8 million acre-feet above what those reservoirs held on June 30, 1977, which was the year when statewide storage ultimately fell to a record-low end-of-month volume of 7.5 million acre-feet at the end of October.
Finally, the punishing Western drought has been accompanied by record-setting high temperatures. The most recent northward shift in heat occurred as monsoon-related showers intensified across the Southwest. By July 19, Glasgow, Montana, reported a maximum temperature of 110°F—the highest reading in that location since July 18, 1936. Glasgow’s third-highest temperature (tied with June 17, 1933) on record, behind only 113°F on July 31, 1900, and 112°F on July 18, 1936.
The High Plains
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Scattered showers largely ended early in the drought-monitoring period. Meanwhile, extreme heat returned across northern portions of the region.
Agricultural drought impacts across the northern High Plains remained widespread and severe, despite spotty showers. According to the U.S. Department of Agriculture, topsoil moisture on July 18 was rated 86 percent very short to short in North Dakota, along with 84 percent in South Dakota and 74 percent in Wyoming.
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Rangeland and pastures were rated at least one-half very poor to poor in Wyoming and the Dakotas, led by South Dakota at 78 percent. On July 18, North Dakota was the national leader in oats rated very poor to poor (50 percent; tied with South Dakota), along with soybeans (41 percent) and corn (32 percent). South Dakota led the nation, among major production states, in sorghum rated very poor to poor (29 percent).
Nationally, the U.S. spring wheat crop was rated just 11 percent good to excellent and 63 percent very poor to poor on July 18, the lowest overall condition at this time of year since July 18, 1988, when the crop was categorized as 7 percent good to excellent and 73 percent very poor to poor. The USDA’s initial estimates on July 12 indicated that the 2021 U.S. spring wheat production would be down 41 percent from last year, while yield will be down 37 percent. If realized, the 2021 U.S. spring wheat yield of 30.7 bushels per acre would be the lowest since 2002. — UNL Drought Monitor
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