So in August or later
Take the opportunity to sow a final round of fast-growing vegetables after the holidays, and enjoy tender lettuce leaves, arugula, and sugar snap peas throughout the autumn. August is still a great month to sow fast-growing vegetables like lettuce, radishes, and Asian leafy greens. Even trendy "micro greens", which are different types of lettuce such as leaf lettuce, arugula, beetroot, basil, and spinach that are harvested when the leaves are small, can be successfully sown outdoors now. You can grow micro greens in a raised bed, pot, or on a windowsill, depending on what suits you.
So later in the fall for an early start to spring
Right before the ground freezes, you can prepare for an early start in your kitchen garden. The seeds will then lie dormant without sprouting through the winter, and will sprout extra early when the light and warmth return. Vegetables and herbs that can be grown this way include chives, carrots, onion seeds (not sets), spring onions, wild garlic, dill, parsley, and parsnips. Be sure to weed and aerate the soil well. If the soil is too compact and holds onto water too well, you risk the seeds rotting if it's a wet winter. Adding a bit of sand to the seed rows topped with seed soil gives the seeds a good bed to overwinter in. Water gently, preferably with a sprinkler head on the watering can, cover with fleece or leaves, and let nature do the rest. When the warmth comes, help with watering again. It can be a good idea to mark what you have sown - it's easy to forget during the winter.
Finished plants
You can also extend the season by filling pots and pallet crates with ready plants of chili, peppers, lingonberries, and herbs. Then you take the shortcut to a good harvest. When it becomes unsafe for night frost, first and foremost chili, peppers, and basil must move inside, but they can continue to grow and provide a good yield indoors as well. When the days get shorter, you will need a growth lamp.