We chose the Journey Series 20 as our favorite hydration pack last year largely due to its performance in hot weather: Its 3-liter reservoir is insulated, so your water stays icy-cold for hours, and the trampoline backpanel helps mitigate back sweat. (The Journey is also ultradurable and highly water-resistant, making it ready for pretty much any type of dayhiking terrain.) Our only major complaint? This is one expensive pack for its size. So thats why this deal at REI is a no-brainer: At 50 percent off, the Journey is no longer in "splurge" territory, and is great buy for anyone who frequently hikes in the heat. Scoop it up now for $99, and start researching trails to take it on.