We have the Bjorn Active Carrier, which is deisgned to be easier on your back than the regular ones. After using my friend's Bjorn, I can agree that the Active Carrier is much better. I wore mine in WDW in May (5/19-5/25) and June (6/7-6/21) and I found my daughter stayed cooler in the Bjorn than in her stroller. I, on the other hand, did not, since ht eextra back support can really make you sweaty. May was much better than June and I really have no complaints about wearing it then. June, however, was a weather nightmare, incredibly hot and humid everyday. Still, it wasn't really any worse than not wearing it. To cover her legs and arms, I used a white receiving blanket, which I tucked in the top of the Bjorn and then draped it over the back. Not only did it keep her arms and legs out of the sun, (which let me dress her in short sleeves/short legs since I didn't have to worry about sun exposure and burning), but it covered the whole Bjorn surface in white, which made it cooler for her than if the sun were beating on the black Bjorn. I also put a sun hat with a visor and neck flaps on her, so she was pretty much totally shaded all day. I also used sunblock since her pediatrician said it was okay to use even though she was under 6 months (almost 3 months and almost 4 months on our trips). Even though she was able to hold her head up by then, I kept her facing me to keep more sun away from her. On most show-type attractions, I took her out completely, but on some rides I would either sit sideways or face her out so she could see what was going on. She's 5 1/2 months now and I generally face her out, but still face her in when she's sleepy and she'll fall asleep pretty quickly when she's in that position. So yeah, it was warm to wear it in June, but May wasn't bad at all, so if the weather is similar for your trip, you'll be fine with a Bjorn.