Night feeding l?

We use condensed formula! So we pre make bottles and store in fridge then in middle of night we just warm a bottle and it’s good to go in our own home.

Well this weekend we are going to my in laws. And I was thinking if we use powdered formula can we put the water in the bottles store in our room then when LO wakes up just add the powder and feed?

Just so we Arnt waking up the whole house wandering around going down 2 flights of stairs to the kitchen?

Does the water have to be warm for it to mix together evenly or is room temp okay?