A cool April in the U.S. southern Plains and Delta region will slow some planting of corn, soybeans and other crops but below-normal rainfall across the main crop belt should prevent any major planting delays this spring, an agricultural meteorologist said on Thursday.

"We'll see delays continue across some southern areas but when you get into the major production areas I don't think we're going to have any major delays," Kyle Tapley with MDA Weather Services told a spring outlook conference.

Tapley also said mild temperatures and timely rains across the Corn Belt this summer, other than some dryness in the western belt, will be favorable for crops and likely produce strong yields.

If realized, this would be the third straight year of generally mild summer weather and bumper crops for the United States, the world's largest top food exporter. This would follow the worst drought in half a century seen in 2012.

In years similar to this spring, corn yields averaged 1.9 percent above the trend and soybean yields were 3.6 percent higher, Tapley said.

MDA forecast the national corn yield at 167.5 bushels per acre and soybeans at 45.9 bpa. In 2014, the average corn yield was 171.0 and soybeans was 47.8 - both record highs.

During March, wet fields in the southern states of Mississippi, Louisiana, Texas and Arkansas have slowed corn planting, which is now running a couple weeks behind normal.

High-tech planters, seeding more than 30 rows on one sweep, allow farmers to catch up quickly. But if corn planting gets too far behind, more acres could be seeded to soybeans, a crop with a shorter growing season that is planted after corn.

Analysts are already forecasting U.S. farmers could plant 3 million or more acres to soybeans than in 2014 given the higher costs to plant corn compared to beans, which need less costly nitrogen fertilizers key to corn yields.

The U.S. Department of Agriculture will release its first 2015 planting estimates based on farmer surveys on March 31.

El Nino, a warming of the southern Pacific Ocean, which is currently in a neutral to weak state, indicates mostly favorable growing conditions for the central United States.

But Tapley said there are concerns about drier than normal conditions in the central and northern Plains, which could stress hard red winter wheat as it breaks dormancy and affect corn and spring wheat plantings.