Here in the Inland Northwest, our weather is extremely variable.
Here are several ways to motivate your tomatoes to ripen their fruit. Remember that the plants main purpose in life, is to procreate and it panics when you do one or more of the following:
Cut back on watering
Shovel pruning – cut the roots about a foot from the plants on two sides. If it’s really late in the season, do all four sides.
Start picking off extra blossoms. One caveat: if it is a cherry tomato leave them alone since they take very little time to go from blossom to ripe fruit.
Pick off tomatoes that you know aren’t going to have enough time to get big enough. These would be the very large, whopper size tomatoes such as Mortgage Lifter, Aussie, Big Rainbow, Rose etc.
Pinch off growing tips as to focus their attention into ripening what they have
Watch the weather like a hawk protect the plants with row cover, bed sheets, tarps, blankets, anything to keep the frost off the fruit.
Here we have used blue tarps.
Once frost touches the fruit they will rot rather than ripen.
This what a frost damaged tomato looks like.
Before a hard, plant killing frost, pick all green ones and bring them inside, most will ripen, the rest you can use for fried green tomatoes or a green tomato relish.