Heavy spring rains in late April and early May erased drought in the central U.S., but also flooded fields forcing many to replant a large percentage of their crop. June followed with the other extreme as many in Illinois received less than 75% of their normal rainfall.
- Total accumulated precipitation in June was 40-60% below average in parts of central Illinois and across fields near St. Louis, as seen in Figure 1.
- Delays in planting and replanting due to flooding have resulted in a very uneven crop across the state. This will spread the pollination time period out over the whole month of July unlike 2014-2016 pollinations, which saw a concentration in the first two weeks of the month.
- The USDA crop progress report for Illinois show good to excellent crops are well behind 2016 progress.
- In late June, U.S. crop conditions were reported at 67% good to excellent which weakly correlates to a slightly below trend yield, as seen in Figure 2.
- Damaging wind and hail reports are above the 10-year average across the country.
- Central Illinois has seen the emergence of Japanese beetles and scouting has revealed damage.
Weather Outlook for July – the Ridge
Long-range forecast guidance from top U.S. and European models agree a large ridge in the flow of the jet stream will establish itself over the western Plains and Rocky Mountains for most of the first three weeks of July. The position of this ridge is crucial to the health of the corn and soybean crops.
- The northern Plains in the Dakotas and Montana are already struggling with drought. This ridge will favor continued dry, warm weather in that region further reducing yields in this part of the Corn Belt.
- With the ridge centered over the mountains, most of the Corn Belt – especially the eastern Corn Belt – will likely benefit from ridge riding storms due to northwest flow aloft in the jet stream. These storms will be hit or miss though, and could contain strong straight-line winds.
- Most of the well-above-average temperatures will stay in the western Plains closer to the axis of the ridge. The heat may migrate east at times and occupy the Midwest, but sustained 10-20 day stretches of well-above-normal temperatures are not expected this July in the Midwest.
- The Gulf of Mexico will remain open for most days allowing for the return of moisture to provide for thunderstorm development.