Keeping LO cool without aircon

Hi mummies, how do you keep your LO cool without depending on aircon? My LO will get angry when he is feeling hot on his back so we had been letting him sleep in his sarong in the day. At night we will turn the aircon on so he have no problem sleeping in his bed. But as he is 4 months old now, he start moving alot in his sarong. (For some reason, he like to face down in his sarong in tummy time position). I wanted him to drop the habit and sleep in his own bed in the day but do not like the idea of having the aircon on 24hr as it will dry up his skin. Any good suggestion from mummies will be much appreciated! Thanks in advance. ?