Wheat was poised for a fourth week of gains, with prices underpinned by concerns over drought affecting some US wheat belts.
Soybeans and corn are also set to notch up a weekly rise, as dry weather threatens the yield prospects of both crops, while there was uncertainty over how much corn Brazil will grow this year.
Broad losses in equity and commodity markets, following a fresh sell-off on Wall Street on Thursday, also kept US grain futures subdued in overnight trading.
The Chicago Board Of Trade most-active wheat contract was down 1.0 percent at $4.51-3/4 a bushel, after reaching a six-month high at $4.64-1/2 on Thursday.
Soybeans were down 0.5 percent at $9.83-1/4 a bushel, after touching a one-week high a day earlier. Corn was 0.5 percent lower at $3.64 a bushel after hitting its highest since mid-August on Thursday at $3.67-3/4.
Grain markets were assessing monthly world crop forecasts from the US Department of Agriculture (USDA), issued on Thursday.
"The USDA's February report came without fireworks and was largely in line with expectations," Rabobank analysts said.
"Argentina weather will remain a key focus over the coming weeks, as dry conditions are expected to return."
Argentina's main crop belt is enduring drought and dry, hot conditions are expected to build next week after some light rain forecast for late this week.
The USDA cut projected Argentine corn and soybean production, while raising its outlook for the Brazilian soybean crop.
Analysts said the USDA made moderate adjustments for Argentina compared to other crop forecasters.
Analysts also stressed that USDA left unchanged its forecast for Brazil's corn output in 2017/18 at 95 million tonnes, well above the 88 million estimated by Brazilian agency CONAB on Thursday.
Corn futures were supported on Thursday by the USDA's cut to projected US stocks, linked to an upward revision to exports.
It increased forecast wheat and soybean stocks, however, as its trimmed export projections.
Wheat remained supported by weather risks, with a winter storm moving through the US Midwest adding a potential threat, while investors have large short positions.
"Short investors probably continue to lurk as potential buyers but their position is probably much smaller by now," said Tobin Gorey, director of agricultural strategy at Commonwealth Bank of Australia, referring to CBOT wheat.