Generally, no, they do not. My kids use them almost daily all summer long and one of their biggest complaints is hot water in the tube. To combat that, you can get an insulated tube cover (designed for snow) to keep the water in your hydration tube cool. Additionally, when my kids have long bike rides in the heat, they always fill their hydration bladder as full as possible with ice and then top it off with water. That usually stays cool for a few hours.