The USDA in its weekly crop progress and conditions report due at 3 p.m. CDT (2000 GMT) was also expected to show the soybean harvest as 11 percent complete, according to the average of analyst estimates.
Soybean harvest estimates ranged from 7 percent to 15 percent and corn harvest estimates ranged from 15 percent to 20 percent.
Heavy rains slowed early fieldwork in parts of the northern Midwest last week, including northern Iowa and southern Minnesota.
Analysts on average expected the USDA to rate 73 percent of the US corn crop in good to excellent condition, down from 74 percent a week earlier.
They expected the government to rate 72 percent of the soybean crop as good to excellent, down from 73 percent the previous week.
Planting of the 2017 US winter wheat crop was estimated at 32 percent complete, up from 17 percent the previous week.