A weekly tracker of the nation's worst drought in decades says parched conditions continue easing in key Midwest states as farmers step up their corn harvests.

The U.S. Drought Monitor update released Thursday says recent rainfall that benefited portions of the Corn Belt came too late to help already damaged corn crops. But the moisture may plump up still-maturing soybeans.

The report shows about one-fifth of the contiguous U.S. remains in the two worst categories of drought - extreme and exceptional. The swath still dealing with exceptional drop dropped by less than half of a percentage point, to 5.96%.

The amount of Kansas still in the worst drought classification fell by 9%age points to 51.04%. Missouri and Arkansas showed improvement in the extreme or excessive drought categories.