CHICAGO (Dow Jones)--Corn futures on the Chicago Board of Trade drifted lower Friday, backpedaling from earlier gains on a lack of fresh supportive news to underpin prices.

September corn ended down 2 cents at $3.21 a bushel, and December corn ended 1/4 cent lower at $3.29 a bushel. In pit trades, speculative fund selling was estimated at 2,000 lots.

The old theory that rain makes grain was a bearish influence on prices, with prospects for big crops anchoring prices, said Don Roose, president of U.S. Commodities.

The absence of a frost threat raised speculation of rising carryout forecasts, with an extended growing season potentially producing record crops in 2009.

The market already has big stocks to buffer any setback in yields, so a strong finish to the growing season only adds to large supplies, Roose said.

The market seemingly moved into a safe zone, with traders unwilling to push prices in the face of big inventories.

Mixed activity in outside markets provided limited leadership during the day, while spillover support from soybeans was an underpinning feature to limit downside movement.

Meanwhile, T-storm Weather said unseasonably cool weather occurs this weekend and into early next week in the U.S. Midwest. Low temperatures in the 40s Fahrenheit will be common with a few upper-30s F. Frost isn't expected because ground temperatures are too warm despite the cool air mass.

Next week, the central U.S. becomes divided by warmth in the west and coolness in the east. A few thunderstorms occur in the Plains and western Corn Belt, but widespread and heavy rain isn't expected as most stay dry. Frost remains unlikely through at least next weekend. Beyond next weekend, forecasting weather is difficult, but climatology and an expected stalling of the weather pattern means that the risk for an early frost isn't currently higher than usual, T-storm Weather said.

First notice day for September futures is Monday, traders and analysts expect few, if any, deliveries against the September corn contract on first notice day due to strong cash prices and the potential for futures to climb on an early freeze.

Oat futures settled weaker. September oats dropped 5 1/4 cents to $2.10 3/4, and December oats lost 5 cents to $2.25.

Ethanol futures slipped. September ethanol fell 1.5 cents to $1.612 a gallon, and November ethanol finished down 1.2 cents to $1.587.

-By Andrew Johnson Jr., Dow Jones Newswires, (312) 347-4604