The percent of contiguous U.S. land area experiencing exceptional drought in July reached the highest levels in the history of the U.S. Drought Monitor, an official at the National Drought Mitigation Centre at the University of Nebraska-Lincoln said.

Nearly 12 percent of the contiguous United States fell into the "exceptional" classification during the month, peaking at 11.96 percent on July 12. That level of exceptional drought had never before been seen in the monitor's 12-year history, said Brian Fuchs, UNL assistant geoscientist and climatologist at the NDMC.

The monitor uses a ranking system that begins at D0 (abnormal dryness) and moves through D1 (moderate drought), D2 (severe drought), D3 (extreme drought) and D4 (exceptional drought).

Exceptional drought's impacts include widespread crop and pasture losses, as well as shortages of water in reservoirs, streams and wells, creating water emergencies.

Currently, 18 percent of the country is classified as under either extreme or exceptional drought, Fuchs said. Much of it is in the south, particularly Texas, where the entire state is experiencing drought -- three-fourths considered exceptional.

The most recent drought monitor report, released late last week, indicated that 59 percent of the United States was drought-free, while 41 percent faced some form of abnormal dryness or drought. Two weeks ago, 64 percent of the country was drought-free.

Other states that are at least 85 percent abnormally dry or in drought according to the report include:

• New Mexico (100 percent in drought, 48 percent exceptional)
• Louisiana (100 percent abnormally dry or in drought, 33 percent exceptional)
• Oklahoma (100 percent abnormally dry or in drought, 52 percent exceptional)
• South Carolina (97 percent abnormally dry or in drought, 16 percent extreme to exceptional)
• Georgia (95 percent abnormally dry or in drought, 68 percent extreme to exceptional)
• Arkansas (96 percent abnormally dry or in drought, 6 percent extreme to exceptional)
• Florida (89 percent abnormally dry or in drought, 20 percent extreme to exceptional)

In the next two to three weeks, some affected areas may see some improvement. The wake of Tropical Storm Don should result in rainfall in the central and western Gulf Coast states, but the degree of drought relief will depend upon the storm's intensity, as well as its track and speed.

"Whenever there is a lot of moisture in a short period of time, the potential exists for rapid improvement," Fuchs said. "But while that possibility exists, it won't necessarily mean the end of drought in those areas. It will likely only improve by one drought category for those areas not impacted by any tropical storms or where drought related impacts improve."

The drought monitor combines numeric measures of drought and experts' best judgment into a weekly map. It is produced by the NDMC, the U.S. Department of Agriculture and the National Oceanic and Atmospheric Administration and incorporates review from 300 climatologists, extension agents and others across the nation.

Each week the previous map is revised based on rain, snow and other events, observers' reports of how drought is affecting crops, wildlife and other indicators.