Rains that began in mid-August and continued into early September "provided much needed relief to parched areas of the Midwest and Southeast," President Reagan's interagency drought committee said Friday.

"These rains provided little benefit to this year's grain crop due to their occurrence late in the growing season, but they will improve forage supplies and soil moisture conditions for 1989 crops," the committee report said.The report was the fourth since the committee was formed in mid-June. A final summation will be prepared in December, the report said.

"In recent weeks, the focus of the 1988 drought has shifted from agriculture to the severe wildfires in the far West," the report said.

"Nationwide, over 68,000 wildfires have destroyed over 4.1 million acres," it added. "As a result of excessive heat and dryness in the West, no relief is expected in the near term for the nation's forests. The economic impact of forest damage this year will extend into future years."

In the case of agriculture, the drought caused crop damage and other losses that are estimated to total about $14 billion to $16 billion this year in terms of 1982 farm prices, the report said. However, the net cash income of farmers is expected to be about equal to last year's level because of sales from inventory stocks and higher commodity prices.

The committee, headed by Agriculture Secretary Richard E. Lyng, included Interior Secretary Donald Hodel and representatives of the vice president's office, the Army Corps of Engineers, the Energy Department, the Tennesee Valley Authority, the Office of Management and Budget and the Federal Emergency Management Agency.