Chicago Board of Trade (CBOT) grains futures closed lower on Monday as favorable weather forecasts led to massive selling during the session.

The most active corn contract for December delivery dropped 3.25 cents, or 0.84 percent, to 3.8475 dollars per bushel. September wheat delivery went down 6.5 cents, or 1.35 percent to 4.745 dollars per bushel. November soybeans slid 5.75 cents, or 0.57 percent, to 10.0725 dollars per bushel.

CBOT brokers reported that funds have sold 7,000 contracts of corn, 4,000 contracts of soybeans, and 3,200 contracts of wheat.

Forecasts for beneficial weather for crop development prompted the massive selling. High temperatures have already eased and expected rains across the U.S. Midwest added pressure on futures prices, following persistent trend of below normal rainfall and above normal temperatures earlier this month, said analysts.

In the latest crop progress report released after the market closure, the U.S. Department of Agriculture said condition rating for the nation's corn crop declined again this week, but there's improvement in the soybean fields.

The report issued Monday afternoon showed 61 percent of corn was good to excellent, down one percentage point from last week.

Soybeans saw a two point improvement overall with 59 percent good to excellent, while spring wheat conditions continued to struggle with another two point drop in condition rating.

The latest crop ratings will give traders new leads for the coming session.