The bottom line: With the weather getting less predictable, job one is to protect tender plants such as tomatoes from frost with sheets or covers to keep them ripening on the vine as long as possible.
As the weather cools, this is a good time to dig and prepare new beds for the spring or build additional raised beds and fill with amended soil.
Pot up selections of your favorite, healthiest herbs in planters to bring inside for the winter. Continue planting cool-season vegetables for winter harvest.
Keep pulling up finished plants and discarding fallen or rotten fruit to discourage overwintering of insect larvae (meaning they stay alive underground through the cold months ahead). Check that the mulch is layered thick enough on cold-season crops.
Some plants will keep producing even through light frosts. Others will continue only if protected overnight with covers. Green tomatoes can be picked and wrapped individually in newspaper and stored in a cool spot (55º to 60ºF) to ripen. If frost is predicted nightly and your tomato plants are covered with unripe fruit, you can pull the whole plant up by the roots and hang it upside down in a protected place like a garage, where fruit will continue ripen on the vine. Promptly remove any tomatoes that go bad.