Crops are either getting too much or too little rain. Either way, the outcome is the same: no food coming from the fields.

Two 500-Year Floods Within 15 Years-- What are the Odds
The term "500-year flood" has been used to describe the recent flooding in the Midwest. Midwesterners who experienced the Great Flood of 1993 - said to be a 500-year flood at the time - can hardly be faulted for thinking they were off the hook for seeing that designation again for, say, a few hundred years.

"The term ‘500-year flood'' can be a little misleading," said Robert Holmes, USGS National Flood Specialist. "We hydrologists realize the term has instant public recognition and we use it to point to the extraordinary nature of such floods. However, the occurrence of a 500-year flood doesn't depend on what happened last year or 15 years ago or 100 years ago. It's based on the annual likelihood of the degree of flooding – in other words, the odds. A 500-year flooding event has a 0.2% chance – 1 in 500 – of happening in any given year in a particular location. A 100-year flood has a 1% chance – 1 in 100 – of happening in the same place, and so on.