Three days from now would be much too long. There are cat viruses that can cause limping, as well as other things. Our cat recently had this issue.
Anytime a cat or dog doesn't want to eat, or is lethargic, is time to take the animal to the vet.
But, describing her being so limp she is almost "lifeless" shows she is really sick. I think you can tell from your own description that your cat needs to be seen by the vet, sooner rather than later. Hopefully, she will be O.K. overnight but I would call the E-Vet, and tell them what is going on.
Bad rainstorms have nothing to do with this.
I would definitely NOT wait three days. This cat is sick.