It’s not safe to eat rhubarb that has been hit by frost as is likely to happen overnight Friday-Saturday.
Oxalic acid, which is always in the leaves and is why leaves ought not be eaten, moves into the stalks after a frost.
It can cause permanent kidney damage.
The University of Illinois has issued a consumer alert on this issue following cold weather there.
If frost has left leaves wilted, don’t harvest those stalks.