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Midwest Weekly Highlights - May 18-24, 2021

Warm Weather Returns

After a cool first half of May, warm weather returned in full force during the period (Figure 1).  Average temperatures in the Upper Midwest were 8-12°F above normal, while most of the Ohio River Valley and Missouri were 2-6°F above normal.  A high-pressure system over the Deep South allowed very warm air to move into the region, while keeping skies sunny for warmer daytime temperatures.  However, minimum temperatures were the main contributor to the warmth, with most of the more than 260 daily temperature records broken coming from high minimum temperatures (Figure 2).

Precipitation to the West

The presence of a high-pressure system across the deep south and extending into the Ohio River Valley kept most of the period’s precipitation in the western third of the region (Figure 3).  Amounts of 1-2 inches were recorded across Missouri, Iowa, west-central Illinois, northern Wisconsin and eastern Minnesota.  Meanwhile, most of the Ohio River Valley and Lower Michigan had less than half an inch.  In eastern Minnesota and northern Wisconsin, totals were more than twice the normal amount (Figure 4), while Kentucky and most of Indiana and Ohio had less than half of normal.

May 19 Minnesota Tornadoes

Several tornadoes were reported on May 19 in southeastern Minnesota as storms impacted the Upper Midwest (Figure 5).  Reports came from Scott County, Rice County and Steele County.  These tornadoes largely impacted rural areas and caused light structural damage and tree damage.  No injuries were reported.  This was the only organized severe weather event during the period, with just a few other reports during the period.

Severe Drought Introduced in Illinois, Michigan

Severe Drought was introduced into extreme northeastern Illinois and southwestern Michigan according to the May 18 U.S. Drought Monitor (Figure 6).  Continuation of very dry conditions along with increased heat and water demand contributed to the introduction of severe drought.  In northeastern Illinois, drought impacted the northern suburbs of Chicago, where soil moistures were very low.  Elsewhere, southern Minnesota saw an expansion of moderate drought before moderate to heavy rainfall impacted the western third of the region. In total, more than 20 million people are estimated to be living in drought-affected areas in the Midwest.