WHEAT - Down 4 cents to 6 cents per bushel

* Wheat futures face bearish headwinds from seasonal harvest pressure and light demand from overseas buyers.

* CBOT September soft red winter wheat last traded down 4-3/4 cents at $4.92-1/2 a bushel, just above the session low of $4.91-3/4 a bushel. K.C. September hard red winter wheat was last down 3-1/2 cents at $4.30 a bushel and MGEX September spring wheat last traded 3-1/4 cents lower at $5.25-1/2.

CORN - Down 3 cents to 5 cents per bushel

* Corn facing pressure from forecast that call for above-average rains and below-average temperatures in key growing areas of the Midwest during the next two weeks, ideal conditions for crop development.

* Corn futures ended overnight trading near their session lows. Most-active CBOT December corn futures contract hit its lowest since May 24 ahead of the break.

* CBOT December corn last traded down 3-1/4 cents at $4.17-3/4 a bushel.

SOYBEANS - Down 4 cents to 6 cents per bushel

* Weather forecast also weighs on soybean market in addition to concerns about trade war with China.

* Traders watching to see if most-active November contract can hold support above the near six-week low it hit on Tuesday.

* US and Chinese negotiators wrapped up a brief round of trade talks on Wednesday that Beijing described as "constructive," including discussion of further purchases of American farm goods and an agreement to reconvene in September.

* CBOT November soybeans last traded down 4-3/4 cents at $8.92 a bushel.