ST. PAUL, Minn. (AP) - Minnesota farmers who have had trouble completing their spring planting due to a muddy May are facing some important decisions this month, and grain prices are rising as traders worry that yields will be hurt by the late finish to the planting season. About 1.2 million acres of corn has yet to be seeded in Minnesota, a full month after it normally would have been in the ground. And nearly half the state's soybean acres have yet to be planted, the U.S. Department of Agriculture reported Monday. "That's not a very good situation for either," said Seth Naeve, a soybean specialist at the University of Minnesota. Two successive weeks of cold, wet weather put the brakes on what was rapid planting progress across Minnesota during the week of May 12. The USDA said 87 percent of the state's corn crop has been planted, while for soybeans, it's 55 percent, both well behind the five-year averages. Southeastern Minnesota has been particularly wet, and there's more rain in the forecast for most of this week, though central Minnesota has been spared some of the heaviest rains and crops there are doing better. "It wouldn't be so serious if the weather was really turning around and we thought we had good warm, sunny days coming up," Naeve said. Given Minnesota's short growing season, corn yields decline rapidly for every day of planting past mid-May. If corn isn't planted "by about June 10, most of the corn agronomists up here recommend we just give up on corn," Naeve said. Soybean farmers have a wider window to plant, but the clock is ticking for them, too. The university's data show that soybeans planted on June 10 lose 25 percent of their potential yield, Naeve said. David Nicolai, a University of Minnesota Extension crop educator in Farmington, said that for soybeans planted after June 10, farmers should use hybrid seed that's tailored to a shorter season. But typically, that seed will lead to lower yields, he said. Jim Schlegel farms in southeastern Minnesota. He said it's been the wettest spring he's ever seen, and he's 83 years old. Even with the bad weather, though, Schlegel was able to resume planting this week, but had to closely monitor his tractor so that it didn't get stuck in the fields. It's been so wet that the hot joke is that farmers are seeing standing water on hillsides, Schlegel said. But while it's been rainy, not every part of Minnesota has had such serious weather problems. "If we can keep getting the rains and warmer temperatures there's a very good potential of having a pretty decent crop coming up this fall," said Francis Buschette, who has retired from farming in Renville County but still keeps a close eye on crop progress. Other Midwestern states have seen similar variable weather patterns. The wettest fields are in Minnesota, Iowa, Wisconsin and parts of Illinois. Indiana and Ohio are seeing near perfect spring planting conditions, but portions of Nebraska and Kansas still have extreme or exceptional drought. The possibility of reduced supplies is affecting grain prices, said Christian Mayer with Northstar Commodity in Minneapolis. "Just a few weeks ago the corn price was quite a bit lower," Mayer said. "Now it's starting to work a little bit higher." Corn prices have risen about 10 percent just in the last week and a half, Mayer said, mainly because of weather concerns.