Fall is a perfect time for gardening. And considering how the spring weather treated us I think we can be assured that fall has to be much better. The variety of crops is limited for fall planting, simply due to the length of the remaining season. And also due to the fact that unlike spring planting when temperatures are increasing, in the fall temperatures are declining and day length is shortening. Which means you'll need to consider which crops will grow under those conditions.
Traditional fall crops include lettuce, spinach, swiss chard, carrots, turnip, radish, cole crops, beets, kale, kohlrabi and onions. Some of these crops can be planted now, while for others it's too late. Some of these crops handle cold weather better than others. However, once daylight gets limited, the crops will no longer grow. So if you want to continue harvest during the coldest part of the season, the secret is to get the plants at a harvestable stage prior to when day length become too short for growth. In mid November, length of daylight dips below 10 hours per day, which is about the limit for any growth to occur. Besides less hours of daylight, the angle of the sun is much lower on the horizon, which weakens the effects of the sun.
Each of these crops has differing levels of cold tolerance. Spinach, onion, kale and radish will tolerate colder temperatures (they can take a hard frost) than will beets, carrots and lettuce (which can withstand a light frost). You can plan your fall garden to harvest certain crops before frosts ends the season (unless you utilize some covering for protection). You'll also want to consider succession planting as once the crop is harvested, you'll not get another harvest from it during winter.
You'll need some protection if your intent is to harvest into the new year. Low tunnels, row covers and poly plastic can all be utilized to provide ample protection for cold hardy plants to be harvested during the winter months. For instance, spinach will continue to live regardless of our winter temperatures, given adequate protection. And as I stated above, that protection can simply be a row cover and poly plastic. A row cover is similar to a sheet. It allows air, sun and water to penetrate, but provide a certain amount of protection by keeping the heat from the soil from being lost to the atmosphere. But it can't provide any heat. So you'll need to place a poly sheet over the row cover once temperatures get low enough that more heat is required. The poly will act like a greenhouse if the sun is present, and temperatures can get quite warm. Of course, you'll need something to anchor these to keep them in place. Bricks, concrete blocks, etc. work great.
Finding seeds may be your biggest hurdle, but there are a few suppliers who still have an assortment. https://web.extension.illinois.edu/registration/?registrationid=12506
If you've never eaten winter spinach, you're in for a treat. Spinach will accumulate higher amounts of sugar in its cells to provide protection from the cold. It's almost like eating candy.