I've been concerned about the lower outside temperatures we've had these past few days.
Many of us know that the virus's viability decays on cardboard significantly in 24 hours. Those tests were done at room temperatures. Given the weather I was interested in what happens at lower temperatures.
I found some answers here. The original paper is cited there and is supported by this paper.
In short, cooler temperatures increase the time the virus is viable. This study was done on stainless steel so no direction for cardboard.
Unfortunately I have no clear cut guidance to give you for the time to wait for items left outside during these lower temperatures. It depends on both the temperature and the surface and I can't find the data to support specific guidance.
If you can put items in an isolated heated space that would be better.