The first half of May was both cool and wet. Preliminary data indicates that statewide temperatures were 1.4 °F below normal for the period May 1-17. Meanwhile, precipitation has been abundant. The statewide average precipitation was 4.15 inches, 1.79 inches above normal or 176 percent of normal. The heaviest rains have fallen in western and northern Illinois. The largest month-to-date total reported was 8.24 inches in Dallas City (along the Mississippi River between Quincy and Moline) by a CoCoRaHS observer.
| Climate Region | Precipitation (in) | Normal (in) | Departure (percent) |
| Northwest | 4.64 | 2.25 | 206 |
| Northeast | 4.55 | 2.06 | 221 |
| West | 5.84 | 2.46 | 238 |
| Central | 4.17 | 2.32 | 179 |
| East | 3.17 | 2.21 | 143 |
| South Southwest | 4.26 | 2.43 | 175 |
| South Southeast | 3.67 | 2.46 | 149 |
| Southwest | 3.37 | 2.49 | 135 |
| Southeast | 3.51 | 2.66 | 132 |
| State | 4.15 | 2.36 | 176 |
Illinois was surrounded on three sides by very wet conditions in parts of Missouri, Iowa, Wisconsin, as well as Kentucky. The rains in Illinois have produced saturated soils in places and minor to moderate flooding along the Mississippi and Illinois Rivers and their tributaries.
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