What temperature requires me to bring my green tomatoes inside to ripen?
This year was a slow year for plants to get started and for things to ripen. My tomatoes didn’t start turning red until almost the end of August, which is much later than usual. So anyone growing tomatoes is wondering how many of the late season ripeners we will be able to harvest.
“As late September approaches, gardeners often try to extend the life of their plants by covering with cloth or plastic. Covering plants works well for nearly red tomatoes, but not as well for mature green ones. Though foliage may sometimes be saved, research shows that chilling injury on green fruit occurs at temperatures of 10 degrees celsius and decay losses rise markedly on fruit exposed to 4.5 degrees C. Red ones well on their way to ripening tolerate colder temperatures.” according to Colorado State University ( https://www.colostate.edu/Depts/CoopExt/4DMG/VegFruit/ripening.htm )
According to the National Gardening Association in Vermont: “If a heavy freeze is on its way, go out and pick all the tomatoes. Green tomatoes that have reached about 3/4 of their full size and show some color will eventually ripen, and smaller, immature green ones can be pickled or cooked green.
Some people like to pull up the whole tomato plant and hang it upside down in a dark basement room and let the tomatoes ripen gradually. Another method is to put unripe tomatoes on a shelf and cover them with sheets of newspaper. Every few days check under the newspaper and remove ripe fruits or any that have begun to rot. The newspaper covering helps trap a natural ethylene gas that tomatoes give off, which hastens ripening. Some people wrap each tomato individually, but this causes a lot of work when you want to check for ripe tomatoes: You have to open each one! You can also place tomatoes in a paper bag with an apple or banana. The fruits give off ethylene gas, which helps to speed the tomatoes’ ripening process.” https://www.garden.org/foodguide/browse/veggie/tomatoes_harvesting/374
So with any luck, we will have a few more warm weeks and your tomatoes will have a chance to ripen outside but if not you might want to bring them in and give these methods a whirl.