Soybean prices eased after firming in the last session, when the market was underpinned by dry weather in Argentina and excessive rains in Brazil. Corn jumped to its highest since early December on strong demand.
The Chicago Board of Trade most-active wheat contract had added 0.5 percent to $4.51-1/4 a bushel by GMT after climbing to its highest since Sept. 29 at $4.55-1/4 a bushel.
Soybeans gave up 0.3 percent to $9.88-3/4 a bushel and corn gained 0.2 percent to $3.59-1/2 a bushel, after hitting its highest since Dec. 4 at $3.60 a bushel.
"The gain in wheat prices is more to do with dryness in US Plains," said Phin Ziebell, agribusiness economist at National Australia Bank. "For beans, there was dryness in Argentina earlier and now rains are expected to delay the Brazilian harvest."
Condition ratings for winter wheat declined in January in several southern US Plains states that have been hit by drought, including top producer Kansas, the US Department of Agriculture said on Monday.
The government rated 14 percent of the Kansas winter wheat crop as in good-to-excellent condition, down from 37 percent at the end of December and from 51 percent in the week to Nov. 26.
The drought in Argentina's oilseed belt is expected to reduce production in the world's biggest supplier of soymeal and soyoil.
Argentina received only scattered rain over the weekend, mostly in northern and central portions of the country, meteorologists said. They expect most crop areas to turn drier and warmer than normal this week.
Thunderstorms and rainfall in key soy producing regions could hamper harvesting and delay planting of winter corn in some areas of Brazil, according to a weather forecaster on Monday.
Investors are using this opportunity to boost positions.
"Nothing can rouse the soybean meal bulls quite like a weather scare in Argentina, and the week ended Jan. 23 was a case in point," Karen Braun, a Reuters market analyst wrote in a column.
In the week ended Jan. 23, hedge funds and other money managers increased their net long in CBOT soybean meal futures and options to 33,221 contracts from 8,074 in the prior week, according to data from the US Commodity Futures Trading Commission.
Surging US corn exports this month should gain even more momentum, helped by a weakening dollar and dry weather in key producing countries, traders and analysts said Friday.