Effects from the bushfires ravaging the NSW mid-north coast have forced racing officials to postpone the final four races at Kempsey.

The decision to abandon the back-end of Friday's meeting, including the $40,000 Kempsey Cup (1450m), was made because of the amount of smoke and ash in the air.

Officials felt the air quality was too poor to continue racing.

More than 90 bushfires were blazing across the state on Friday, fanned by gusty winds.