yep, if he will drink it

. It is actually quite a good thing to get them used to having bottles at different temperatures as soon as you can so that if you get stuck somewhere and can't warm a bottle it is not the end of the world.
A friend's DD was really picky and if the bottle cooled too much whilst she was drinking it, she would stop and refuse any more so she often had two smaller bottles so one could be left in some warm water, just in case