If you still have moderate weather with warm days and cool nights, go ahead and add seed to your lawn to fill in bare areas. Look for a seed suitable for your area — sun or shade or mixed. Some seed packages also are indicated for fall.
It is best to seed when it’s not windy. Clear area to expose soil. Apply one half of the total seed mixture in one direction. And the remaining amount at right angles. After seeding, rake the lawn area (light touch with the rake) to mix the seed into the top level of soil.
Keep the surface soil moist. Sprinkle with water set at a low level to keep seeds in place until the seedlings start to grow. And then keep watered on a regular basis if no rain in forecast.
If all works out — you’ll have more grass to mow next spring!