UPDATE Oct. 15, 2020: If you escaped the frost so far this fall, take heed tonight, as temperatures are expected to dip below freezing for much of the eastern third of the state.
Forecasts this week call for possible frost in Iowa from Thursday night, Oct. 1, into Friday morning.
According to Iowa State University Extension & Outreach, the average date of the first 32 degree temperature in Iowa ranges from Sept. 30 in far northwest Iowa to Oct. 15 in the southeast.
By some definitions, a hard, or killing freeze, happens when temperatures remain at a sustained 28 degrees. Given that forecasts predict temperatures in the 30s overnight later this week in Eastern Iowa, many plants should be safe.
As a precaution for tender vegetation, such as some flowers, tomatoes and peppers, a bedsheet or light blanket can be used to cover the plants overnight and removed in the morning, once temperatures have rebounded. Plastic usually isn’t as effective.
If you want to be on the safe side, tomatoes, peppers, cucumbers and other vegetables can be harvested before the predicted frost. Green tomatoes will ripen indoors if kept unrefrigerated.
Plants in containers can be moved into a garage or porch where they will be protected, and returned outdoors once the chance for frost has passed.
Hardier vegetables, such as carrots and kale, can survive a frost and even a freeze. With warmer temperatures on the horizon in the long-term forecast, the gardening season should extend well into October in most parts of Iowa.