ZIP SLEEPING BAGS TOGETHER
Most bag zippers–even on different brands–are compatible, so if you’re buying a new mummy sack for a hot date 15 miles from the trailhead, just make sure your zippers are on opposite sides.
MAKE AN OLD BAG WARMER
Wash it! Dirt and oils accumulate inside sleeping bags over time and inevitably decrease loft–and warmth. Here’s how to clean it: Turn it inside out and wash in a front-loading machine with mild powder soap or Nikwax Down Wash ($9; nikwax.com). Run two rinse cycles, then place in a large dryer with two tennis balls (which prevent the insulation from clumping). When it’s dry, store it suspended from the ceiling or a high hook (so it doesn’t touch the floor) rather than in a stuff sack to protect loft. If all else fails, a removable liner (such as the Cocoon MummyLiner in CoolMax or flannel; $30-$40, designsalt.com) adds a few degrees of warmth and costs less than a new sack.
LAYER FOR EXTREME TEMPERATURE CHANGES
When it’s 70°F by day and 20°F by night (hello, desert in springtime!), think four layers, not three. Always pack a next-to-skin baselayer and a waterproof shell, but split your midlayer into two lightweight, versatile insulation pieces, like a microfleece turtleneck and a puffy vest.