CHICAGO (Dow Jones)-- Chicago Board of Trade corn futures are expected to open lower Monday on outside market pressure and a frost-free weather forecast, analysts said.

Corn is called 4 cents to 6 cents lower. In overnight trade, September corn was down 4 cents to $3.17 per bushel and December corn was down 6 1/2 cents to $3.22 1/2.

Corn and other markets are being pressured by a sharp sell-off in the Chinese equities market, analysts said. Weaker crude oil, which is tied to corn because of ethanol, is among the markets weighing on prices.

Traders said the market was initially firm overnight but broke on the outside pressure.

Otherwise the main focus of the corn market is currently on the weather, which is mostly bearish Monday. A frost threat over the weekend turned out to cause little if any damage in the far northern reaches of the corn belt, in Minnesota and Wisconsin.

Analysts say the market needs a longer-than normal growing season for the crop to reach its full potential. An early frost could cause significant damage.

"I didn't see any meteorologist calling for any (frost) through the 11-to 15-day forecast," a trader said.

Speculative funds cut 9,197 contracts from their CBOT corn long positions and added 12,270 contracts to their short positions, putting them net short 22,952 contracts, the Commodity Futures Trading Commission said Friday.

A trader said the extent of the spec funds' short position was a little bit greater than expected, but that it should have little effect on Monday's trade.

The supplemental commitment of traders report also showed that commercial funds cut 8,148 contracts from their long positions and cut 18,093 contracts from their short positions, putting them net short 189,923 contracts. Index funds cut 3,056 contracts from their long positions and cut 8,745 contracts from their short positions, putting them net long 330,832 contracts, the CFTC said.

Technically, the corn bulls' next upside price objective is to push December prices above solid resistance at $3.50 a bushel, a technical analyst said. The next downside price objective for the bears is to push and close prices below solid technical support at the August low of $3.11 1/2 a bushel.

First resistance for December corn is seen at Friday's high of $3.32 1/2 and then at last week's high of $3.37 1/2. First support is seen at $3.25 and then at last week's low of $3.20 3/4.

Traders and analysts say the market ultimately is likely to make new lows if the benign weather pattern persists through September.

-By Ian Berry, Dow Jones Newswires; 312-341-5778; ian.berry@dowjones.com