While we highly recommend using boiling water (especially if you are out in the backcountry using water collected from rivers/streams/lakes), the meal will rehydrate with warm water. If you are using warm water rather than boiling water, you may need to stir more thoroughly and wait a little longer for the water to be reabsorbed.If you are using cold water, we suggest rehydrating your meal at least 30 minutes before you plan to eat so that the food has fully absorbed the cold water.