Metrorail ridership reached a record high in June, and both bus and subway performance improved over the last fiscal year, according to a Metro report made public yesterday.

The report, which included an account of operating performance and financial data for June as well as a year-end summary of performance for fiscal 1983, noted that Metrorail ridership reached a peak of 314,000 average weekday trips in June.

The year-end total for ridership was 80,780,000 trips, which exceeded Metro ridership for fiscal 1982 by 3 percent.

In a report to the Metro board, General Manager Carmen E. Turner said rail service dependability, measured as miles between service interruptions, was 19,666 miles in June, bringing the annual average to 17,149 miles.

This was an 84 percent improvement over the previous year and well above the 10,000-mile minimum acceptable level established by the board for rail service.

The report on bus service, however, was less glowing, especially in the areas of ridership and bus availability.

Buses averaged 1,074 miles between service interruptions, which was a 12 percent improvement over the previous year but 17.4 percent below the board's fiscal 1983 objective.

Total bus ridership declined 4.3 percent to 130,100,700 trips.

There also were minor declines in several operating statistics for June, with service interruptions up 21.6 percent over the previous June. The report said hot and humid weather in late June of this year caused hot engines and air-conditioner failures that contributed to the increase in service interruptions during this period.

With the exception of bus availability, however, the report said overall bus performance in fiscal 1983 was better than it was in fiscal 1982.

"These service improvements are a direct result of the emphasis the board and staff have placed on service reliability," Turner said. "The programs that we have in place to improve reliability are working."

Financially, the report said, both bus and rail operations were below fiscal 1983 budget estimates.

Metrorail operating assistance was about $4.6 million under budget because of lower costs and higher revenues, and Metrobus operating assistance was about $300,000 under the budget estimate because of lower costs.