* Beneficial rain, cooler weather help many states
* Much of the winter wheat suffers from drought
* Much of Kansas, Nebraska in extreme drought or worse
By Carey Gillam
Nov 15 (Reuters) - A storm system that brought cold, wet weather to much of the United States last week helped ease drought in many states, but some areas that were most in need of moisture were missed, according to a climatology report issued on Thursday.
The U.S. High Plains, which includes key farm states of Nebraska, South Dakota, and Kansas, saw slight improvement last week due to good precipitation. But three quarters of both Kansas and Nebraska continued to suffer from extreme or exceptional drought.
In South Dakota, extreme or worse drought still covers nearly 55 percent of the state.
Roughly 58.83 percent of the contiguous United States was in at least "moderate" drought as of Nov. 13, down from 59.48 percent a week earlier, according to Thursday's Drought Monitor, a weekly compilation of data gathered by federal and academic scientists.
The portion of the contiguous United States under "extreme" or "exceptional" drought - the two most dire classifications - improved to 18.30 percent from 19.36 percent.
The persistent drought has hindered growth of the new winter wheat crop in many U.S. Plains states. The U.S. Department of Agriculture said this week that wheat in Nebraska, South Dakota, and Montana has shown very poor emergence and is well behind the average pace.
Texas and Oklahoma, also key wheat growing states, continued to struggle with drought.
Overall, the new winter wheat crop is rated 36 percent good to excellent, below last year's rating at this time of 50 percent. Kansas wheat is rated 21 percent poor to very poor.
Wheat in Nebraska, South Dakota, Colorado, and Oklahoma is struggling with more than 30 percent of it in each of those states rated poor to very poor, according to USDA.
In Texas, the drought deepened as the state was largely missed by the rain storms that swept through the Plains and Midwest. In contrast, most of Oklahoma, Arkansas, and western Tennessee measured widespread "decent" precipitation, according to the Drought Monitor. (Reporting by Carey Gillam in Kansas City; Editing by Bob Burgdorfer)