Crops have incurred more than $8 billion in estimated weather-related damage thus far in 2008, according to the American Farm Bureau Federation (AFBF). Iowa accounts for about half the damage, but there are notable problems in at least a dozen other states ranging from the excessive wetness and flooding in Illinois to drought in California.

"Wet weather and flooding create issues, as farmers are unable to plant their crops," says Terry Francl, AFBF senior economist. "The crops they do plant do not sprout and grow, resulting in fewer acres harvested. Additionally, the difficult growing conditions greatly reduce the yield of the crop that is harvested." He adds that expected Iowa corn yields are reduced 16% for this year, and 1.5 million to 2 million acres of corn and soybeans in Iowa that farmers intended to plant this spring will likely remain fallow.

This results in a $4-billion shot to Iowa's crops. Other states taking a hit from excessive wetness and flooding are: Illinois, $1.3 billion; Missouri, $900 million; Indiana, $500 million; Nebraska $500 million; and an additional $1 billion in remaining wet states.

Some areas are experiencing the opposite problem. Drought is taking a toll on several Western states and a few states in the Southeast. Northern California battled the driest spring in its history. As a whole, the state suffered $500 million in estimated damage. This equals the estimated drought-related damage in all other states combined.

Nationally, the average corn yield is likely to decline some 8-10 bu./acre from the 2008 trend line, mostly due to inclement weather. The national average soybean yield is also likely to be down 1-2 bu./acre from the current USDA projection of 42.

These damage estimates relate only to crop production as of the last week of June. This means livestock, infrastructure, building and equipment losses aren't considered. Additionally, the estimate assumes normal weather conditions will ensue for the remainder of the growing season. Varying weather conditions later in the season could cause the estimate to grow or contract.