Heat continues to put pressure on drought conditions

This U.S. Drought Monitor saw continued intensification of drought across areas of the Midwest, South, Southwest, and the Pacific Northwest.

In the Midwest, extreme heat impacted areas of the region including Minnesota, Iowa, Missouri, Wisconsin, and Illinois with temperatures soaring 6 to 10+ degrees Fahrenheit above normal. Daily high temperature records were broken across the region during the past week including in Chicago (98), Milwaukee (101), Minneapolis (101), and Des Moines (100).

Areas of the South including the northern Gulf Coast of Texas, Louisiana, and southern Mississippi saw continued drought-related deterioration on this week’s map as the heatwave continued to push high temperatures over 100 degrees with numerous records broken during the past week.

Record daily highs were set or tied in various southern cities including Houston (109), San Antonio (104), Austin (107), Dallas (109), Baton Rouge (106), New Orleans (103), Jackson (106), and Mobile (101). In Louisiana and southern Mississippi, the continued hot and dry conditions have led to numerous wildfire outbreaks as well as widespread poor hydrologic conditions and severe impacts within the agricultural sector.

In the Southwest, monsoon precipitation has been well below normal across much of the region with areas of southern Arizona and New Mexico reporting rainfall deficits ranging from 3 to 6 inches since the beginning of July. In the Pacific Northwest, areas of drought expanded on the map in Oregon, Washington, and Montana in response to a combination of above-normal temperatures over the past 90-day period, precipitation shortfalls, and poor surface water conditions.

Conversely, some areas saw improved drought-related conditions on the map, including southern Texas where heavy rains, in association with Tropical Storm Harold last week, provided much-needed moisture to the region. Rainfall accumulations along the southern Gulf Coast and South Texas Plains regions ranged from 2 to 6 inches.

South

In the South, the heatwave continued across the region during the past week with record-breaking temperatures observed across the eastern half of Texas, Louisiana, and Mississippi. On the map, areas of Extreme Drought (D3) and Exceptional Drought (D4) expanded along the northern Gulf Coast of Texas and Louisiana as well as areas of Severe Drought (D2) and Extreme Drought (D3) in southern Mississippi.

According to the latest U.S. Department of Agriculture Weekly Weather and Crop Progress Bulletin (issued Aug. 29), the percentage of topsoil in Texas rated short to very short was 92%, while neighboring Louisiana was rated 88% short to very short. In addition, Water Data for Texas was reporting (8/30) reservoirs in the Edwards Plateau Climate Division were 35.9% full, while the South-Central Climate Division reservoirs were 44.2% full.

The National Drought Mitigation Center’s Condition Monitoring Observer Reports were reporting hundreds of impact reports from across Louisiana and Mississippi during the past 30 days. This past week, average temperatures across the region were well above normal across most of the region with temperature departures ranging from 2 to 10+ degrees above normal. The region was generally very dry except for some isolated areas of light to moderate accumulations observed in areas of Texas (east Texas, Trans-Pecos), Louisiana, and southern Mississippi.

In south Texas, some locally heavy rainfall was observed in association with Tropical Storm Harold making landfall and providing beneficial rainfall to drought-affected areas.

Midwest

For the week, light precipitation accumulations (less than 2 inches) were observed across areas of Missouri, southern Illinois, southern Indiana, Ohio, and Michigan. On the map, some degradations were made in areas of Iowa, Minnesota, Wisconsin, and Illinois where both short- and long-term precipitation deficits persist. According to the latest USDA Weekly Weather and Crop Progress Bulletin, the percentage of topsoil rated short to very short is as follows: Iowa 68%, Minnesota 60%, Wisconsin 48%, and Illinois 43%. Furthermore, the latest USDA Iowa Crop Progress and Condition report (Aug. 28) noted persistent dry conditions have put stress on crops, especially soybeans, with numerous reports of disease entering fields.

Average temperatures for the week were well above normal (2 to 10+ degrees) across much of the region with the greatest anomalies observed across areas of southern Minnesota, Iowa, Missouri, southern Illinois, and southwestern Wisconsin.

High Plains

On this week’s map, degradations were made in northern portions of North Dakota and in eastern Kansas. Conversely, recent precipitation during the past 30-60-day period led to some minor improvements on the map in drought-affected areas of southeastern Nebraska. Across most of the Plains, hot and dry conditions prevailed this week except for some isolated shower activity along the Kansas-Nebraska border region where 1 to 3 inches of rain were observed. Average temperatures for the week were well above normal (2 to 8 degrees) with the greatest departures observed in northwestern North Dakota and eastern portions of Nebraska and Kansas.

West

On the map, degradations were made across areas of the Southwest and Pacific Northwest including New Mexico and Montana. Poor soil moisture and low streamflow levels led to expansion of Extreme Drought (D3) in northwestern Montana. In New Mexico, the combination of short- and long-term precipitation deficits, poor soil moisture, and impacts in the agricultural sector (eastern New Mexico) led to continued deterioration on the map across parts of the state.

For the week, some light precipitation accumulations (generally under an inch) were observed in isolated areas of the Four Corners states and Intermountain West.

Looking ahead

The NWS WPC 7-Day Quantitative Precipitation Forecast calls for heavy precipitation accumulations ranging from 4 to 10+ inches in association with impacts of Hurricane Idalia, which is forecast to bring very heavy rains across the Big Bend region of Florida as well as across areas of the Coastal Plain of Georgia and the Carolinas.

In the Northeast, dry conditions are expected, while most of the South, Midwest, and the Plains states are forecasted to experience generally dry conditions. In the West, some light to moderate accumulations ranging from 1 to 3 inches are expected across portions of Arizona, Utah, and in isolated areas of the central and northern Rockies.

The CPC 6-10 Day Outlooks call for a moderate-to-high probability of above-normal temperatures across much of the conterminous U.S. in an area extending from the Rocky Mountains to the Eastern Seaboard. Near-normal temperatures are expected over the remainder of the West except in Washington state where temperatures are forecasted to be below normal.

Below-normal precipitation is expected across much of the southern tier of the conterminous U.S. as well as portions of the Mid-Atlantic, Great Basin, and Intermountain West. Meanwhile, above-normal precipitation is forecasted for areas of the Upper Midwest, Northern Plains, and the Pacific Northwest.

David Simeral is with the Western Regional Climate Center.