Tracking overnight losses, the grains opened Wednesday's trade slightly lower on news that rains are falling in South America, improving on the hot, dry crop-stressing weather there.

In early trading, March corn is 2 1/2 cents lower at $6.04 1/2 per bushel, January soybeans are 2 1/4 lower at $11.42 1/2 and March wheat is 6 1/2 lower at $6.01 1/4, according to Barchart.com.

• See more of the latest grain futures prices

The grains are following the weather situation in South America closely this week; earlier in the week, dry, hot conditions were starting to stress the corn and soybean crops in Argentina and Brazil during the critical corn pollination growth period. But, rains have fallen in that part of the world over the last 24 hours, alleviating the weather stress there. But, another new weather outlook Wednesday morning shows it may not be long until that heat stress returns.

• Marketing Talk: Did the rains fall?
• Read more: Rain in S.A. to lower corn prices
• Also: Continued stressful heat in Brazil