How long will it take hair to grow back after shaving?

I have been shaving my arms (I know stupid idea) but I'm going on a trip with my family in 3 weeks 3 days and we are going to my aunts and I can't take a long enuff shower to shave my arms so if today is the last day I shae my arms will the hair be back to normal length in 3 weeks and 3 days