(Updates with closing prices, expectations for conditions report)
CHICAGO, June 12 (Reuters) - U.S. corn futures dropped 2.8 percent on Monday on forecasts for rain that is expected to bolster the health of a crop stressed by adverse weather throughout planting and early development, traders said.
The improving weather view also weighed on wheat and soybean futures as traders used it as an excuse to lock in profits from recent rallies.
"We have a little more precipitation in the forecast," said Chad Henderson, a grain market advisor with Prime Agricultural Consultants. "That's really what is weighing on things."
Chicago Board of Trade soybean futures for July delivery ended down 10-1/2 cents at $3.77-1/4 a bushel. The corn market notched its biggest loss in percentage terms since Nov. 9.
"Confidence building on expected rainfall east of the Mississippi River, but corn and soybeans in the Plains and western Midwest look to miss out," Thomson Reuters Agriculture Research analysts said in an update on Monday.
CBOT May soft red winter wheat futures were 11-3/4 cents lower at $4.34 a bushel.
Wheat still faced pressure from the U.S. Agriculture Department's surprise upward revision to the harvest forecast, issued on Friday.
"Overall, the USDA now expects the renewed surplus on the (world) wheat market to total 4.8 million tons, which is somewhat higher than before. This is pressuring the U.S. wheat price this morning, which had been pulled up last week by the lack of high-quality wheat," Commerzbank analysts said in a note.
CBOT July soybean futures dropped 10-1/4 cents to $9.31-1/4 a bushel.
Traders were waiting for USDA's first report on U.S. soybean conditions. The government's weekly crop progress report, which also will feature corn and spring wheat conditions, will be released at 1500 CDT (2000 GMT) on Monday.
Analysts were expecting the report to show that the soybean crop was rated 70 percent good to excellent. Corn ratings were expected at 67 percent good to excellent, down 1 percentage point from last week, and spring wheat ratings at 53 percent good to excellent, 2 percentage points lower then a week ago. (Additional reporting by Naveen Thukral in Singapore and Gus Trompiz in Paris; Editing by Richard Chang and Chizu Nomiyama)