I leave water for 20 mins after boiling before making up bottles, so the water is not "boiling" but it is still steaming and by no means just warm. If you're gonna store formula in the fridge with the powder mixed in then its important to add it to 70c+ water. Its not ideal but its ok to use cool/warm pre-boiled water, then mix with powder as long as you feed immediatly and not store. xxx