Midwest Overview - April 2012

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Majority of Midwest Experiences Cooler Temperatures in April than March

Despite a majority of the Midwest experiencing above average temperatures during April, many stations across the region experienced cooler temperatures in April than they did in March, which is in great contrast with what is climatologically expected for this region (last column in table below shows normal departure for April versus March). On a statewide averaged basis, five out of the nine states experienced April temperatures that were cooler than March. There were only three states in the Midwest region that experienced a warmer April when compared to March -- Iowa, Minnesota, and Missouri. However, despite the statewide averaged temperature, some stations in eastern Iowa still averaged cooler April temperatures. Dubuque, Iowa (Dubuque County) experienced March temperatures that were 1.3°F warmer than April, which marks the first time this has occurred among the 162 years of record in Dubuque.

Stations within southern Wisconsin, northern Illinois, Indiana, Michigan, western Ohio, and northern Ohio experienced average April temperatures that were 1°F to 3°F below March 2012 average temperatures, representing the greatest negative departures from March temperatures in the region (Figure 1). Unlike the rest of the Midwest, northwest Minnesota experienced April temperatures that were 6°F to 8°F warmer than March temperatures (Table 1).

Average temperatures in April ranged from 60°F to 65°F in southern parts of the region to 35°F to 40°F in northern Minnesota and Michigan (Figure 2), making temperatures near to above normal for a majority of the region (Figure 3). Northern Minnesota and the northeast corner of Ohio were the only regions to experience slightly below average temperatures. Minnesota, Iowa, and Missouri experienced the highest departures from normal, with temperatures 2°F to 6°F above average during April. Several daily temperature records and a few monthly temperature records were set during the month, with a majority of the record high temperatures being set during the unseasonably warm first week of April.
 

Cooler April Brings Damaging Freezing Temperatures

The exceptionally mild weather of March and early April pushed the development of trees and plants as much as one month ahead of schedule in many parts of the Midwest. During the second week of April, freezing temperatures were reintroduced to the region, setting the stage for severe freeze damage for some vegetation and early-emerging crops. The first widespread freezing temperatures occurred on April 10th, 11th, and 12th (Figure 4), with occassional light freezes occuring later in the month throughout the region. The damage to vegetation from freezing April temperatures ranges from light to severe throughout the region, with fruit crop suffering the most in Michigan and Kentucky. There were also scattered reports of damage to early-planted corn crop in Missouri. For much of the region, the extent of damage and economic loss cannot be readily determined at this time.
 

April Precipitation Below Normal in the Eastern Midwest, Above Normal in the West

Precipitation was below normal in April for a majority of the eastern Midwest, while a good portion of the western Midwest experienced near to above normal preciptiation (Figure 5). The west central, north central, and northeast portions of Minnesota received 175%-300% of their normal April precipitation, with the rest of Minnesota experiencing precipitation near the historical average. In Minnesota, this is only the second month since July 2011 where monthly precipitation totals were near to above average. Parts of Missouri and Iowa also received above average preciptiation during April. A band from the southwest corner of Missouri to the east central part of Missouri received at least 5 inches of precipitation during April (Figure 6). However, the southeastern corner of Missouri only received 1.5 to 2 inches of precipitation, which is only 25%-50% of this region's normal April precipitation.

The dry conditions during April in western Kentucky is raising concerns about developing drought conditions as the summer approaches. Only receiving 0.5 inches to 2 inches of precipitation during April (10% to 50% of normal) resulted in the development of Moderate Drought (D1) in western Kentucky throughout the month (Figure 7). Adequate to abundant precipitation totals thus far in spring 2012 have somewhat improved the drought conditions in Minnesota, however drought conditions still persist. Dry conditions in Minnesota during the spring increases the potential for wildfires in this region. The Department of Natural Resources has given several northern Minnesota counties a Moderate fire danger rating. Historically, 80% of all wildfires in Minnesota occur during April or May.

A snowfall event during the third week of April brought over three inches of snow to northeast Minnesota (Figure 8). Northern Wisconsin and Upper Michigan also received 1.5 to 4 inches of snowfall throughout the month, which is anywhere from 2 to 8 inches below normal (Figure 9). Snow was minimal across the rest of the Midwest, representing snowfall that is near to just below normal for the region. In Iowa, there was only one report of snow or sleet during the month, which represents the fewest April snow/sleet reports in Iowa since 1890. Hundreds of daily precipitation records and just under 40 monthly precipitation records were set throughout the month, in addition to a few daily snowfall records.
 

April Brings Severe Weather

One notable severe weather event during April occurred on 14th, when severe thunderstorms made their way across Iowa, bringing many severe weather reports - including two destructive EF-2 tornadoes - to the Hawkeye state. More information on the April 14th severe weather outbreak can be found in the April 8-14 Midwest Weekly Highlights. Severe thunderstorms continued through the region on the 15th and 16th, bringing more tornadoes and high winds to the region, in addition to snowfall in Minnesota (more information can be found in the April 15-21 Midwest Weekly Highlights).

Later in the month, on April 28th, a line of severe thundestorms brought damaging high winds and hail to the southern Midwest. In St. Louis, Missouri, high winds blew down a tent where nearly 200 people were gathered after a Cardinals game, killing one and critically injuring at least five others. The severe weather event on the 28th brought gusts of nearly 90 mph to Indiana, hail the size of softballs to Illinois, and power outages to much of this region, including Kentucky.
 

Planting Progress During April

A majority of farmers in the Midwest typically start planting corn during mid to late April and soybeans are planted late April to early May. Due to warmer weather this spring so far, farmers in all nine Midwest states were able to plant early and as a result, are well above the 2007-2011 average for planting corn and most are above the average for planting soybeans as well. Kentucky and Illinois are furthest along in planting corn, while Indiana and Kentucky are furthest along in planting soybeans (Table 2).

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The Illinois State Climatologist Office also contributed to this report.
The Iowa Climatology Bureau also contributed to this report.
The Kentucky Climate Center also contributed to this report.
The Minnesota State Climatology Office also contributed to this report.