The sleeping bag is light and airy, perfect for warm / hot summer. He feels very pleasant; great material quality! Since we have the sleeping bag I'm not more worried if my son is packed too warm or too cold. Practically I think whatever the sleeping bags where the zipper is to close from top to bottom. I have the feeling that it still might be a bit too warm, I'll go back to the bottom. The pity is that there is no intermediate size in the model. I think the difference between 70 cm and 90 cm simply something big.