Cool-season crops are the vegetables you should look for to grow in the fall. While many need to be planted in late summer, you can still plant seeds through September or even later, depending on your climate.
Radishes are a great place to start if you haven’t tried fall gardening before. They can be harvested in less than a month, allowing you to get multiple harvests before the weather turns too cold. Leafy greens, including lettuces, arugula, cabbage, mustard greens, and spinach, love cool weather and can be harvested in 4-8 weeks, allowing most growing zones plenty of time for succession planting to enjoy greens until it freezes.
Root veggies, including carrots, garlic, onions, potatoes, and beets, are frost-tolerant, so if you’re cutting it close to your frost date, these should stick around after a light freeze.