Temperature difference from normal over the Lower 48 states during April. (WeatherBell.com)

The upper Midwest and Great Lakes states are known for their long, punishing winters. But an abnormally cold April made 2017-2018’s version seem endless.

Temperatures some 8 to 14 degrees below normal, averaged over the entire month, resulted in one of the most frigid Aprils on record in the Dakotas, Minnesota, Iowa, Wisconsin and Michigan.

Temperatures ranked among the top five coldest during the month in most locations in this region, including Minneapolis, Milwaukee, Des Moines and Chicago.


Many locations also received an abnormal amount of snow. Both Minneapolis and Green Bay, Wis., notched their biggest April snows on record between the 13th and 16th.

Here are some specific cold and snowy milestones set at select locations:

  • Chicago had its fourth-coldest April on record. It dropped to 32 degrees or lower on 16 days during the month, the most times on record.
  • Minneapolis had its fourth-coldest April on record. Its 26.1 inches of snow were the most on record, exceeding April 1983’s 21.8 inches.
  • Milwaukee had its fifth-coldest April on record.
  • Madison had its second-coldest April on record (just a tenth of a degree above the coldest average temperature of 37.5 degrees, set in 1874). Its 13.5 inches of snow were also the second most on record in April to 1973’s 17.4 inches.
  • Green Bay had its second coldest April on record (just two-tenths of a degree above the coldest average temperature of 35.3 degrees, set in 1907). Its 36.7 inches of snow were the most on record by a huge margin, over 20 inches above the previous highest amount of 15.1 inches from 1907.
  • Indianapolis dropped to 32 degrees or lower 14 times, the most on record.

Radiant Solutions, a weather consulting firm based in Maryland, posted the April temperature rankings for several additional cities, including some in the Southwest that were, on the flip side, abnormally warm:

The rankings for the April cold in several cities would have been a notch or two more extreme had it not been for a pattern change at the tail end of the month, which brought highs near 80 degrees to many areas. Minneapolis hit 80 on April 30, its warmest day since Sept. 24 last year.

For much of the month, deep pools of abnormally cold air slid south from Canada into the upper Midwest and Great Lakes states. They rode along the jet stream that bulged north over the Western states, bringing abnormal warmth to that region, but then crashed south in the eastern two-thirds of the nation.


April high-altitude weather pattern over Lower 48 show cold pool of air over the upper Midwest, Great Lakes and Northeast, and milder air ridging over the Southwest. (NOAA)

In recent days, the jet stream configuration has reversed, and a dome of warm air is sprawled across the eastern United States, while a cold pool is visiting the West.


GFS model simulation of high-altitude weather pattern on May 2, which shows cold pool of air over the Southwest with warm ridging over the eastern part of the country. (WeatherBell.com)

Because such a large portion of the Lower 48 was under the influence of the cold-weather pattern during April, more than 6,500 low-temperature records were set, compared with just over 2,200 record highs.

While the Lower 48 was, on balance, cold during the month, most of the rest of the Northern Hemisphere was warmer than normal.