Therm-a-Rest Polar Ranger Sleeping Bag
We designed the Polar Ranger sleeping bag for expeditions where failure isn't an option. Rated to -20°F (-29°C), this bag combines water-resistant synthetic insulation with a streamlined mummy shape that locks in warmth without adding unnecessary bulk. The Nikwax Hydrophobic Down™ treatment on the synthetic fill ensures the bag retains loft and thermal efficiency even in damp conditions—critical when you're sleeping in snow caves, winter tents, or high-altitude camps.
The Polar Ranger features our SynergyLink™ Connectors that integrate seamlessly with Therm-a-Rest sleeping pads, eliminating cold spots and keeping you centered on your pad all night. A draft collar and insulated hood with adjustable drawcords seal out frigid air, while the full-length zipper includes a draft tube to prevent heat loss along the closure. Whether you're mountaineering in the Cascades or winter camping in the Rockies, the Polar Ranger delivers reliable warmth when temperatures plummet.
What makes the Polar Ranger winter-ready
Insulation Technology & Moisture Management
The Polar Ranger’s Nikwax Hydrophobic Down™ treatment represents a fundamental shift in how we engineer cold-weather insulation. Unlike untreated synthetic fill that absorbs condensation and body moisture, our treated fibers shed water while maintaining loft. During multi-day winter trips, this moisture resistance becomes critical—each night’s breath and perspiration would otherwise accumulate in the insulation, degrading warmth by the third or fourth night.
We place higher fill weights in the torso and foot box where your body loses heat fastest, a zone-construction approach that delivers warmth where you need it without adding weight to areas that see less heat loss. The shell fabric carries a durable water-repellent finish that sheds tent condensation and light snow, giving you an extra margin of protection when conditions deteriorate.
Fit, Sizing & Pad Integration
The Polar Ranger comes in regular (6 feet) and long (6 feet 6 inches) lengths, each with a mummy taper that eliminates dead air space while still allowing you to shift positions through the night. We cut the shoulder girth at 62 inches and the hip at 58 inches on the regular size, dimensions that accommodate layered clothing without feeling restrictive.
SynergyLink™ Pad Attachment
Our SynergyLink™ Connectors snap directly to compatible Therm-a-Rest sleeping pads, creating a unified sleep system that moves with you. The connectors prevent the common problem of rolling off your pad in the middle of the night—a mistake that costs you the insulation layer between your back and the frozen ground. When paired with a high R-value pad, the system delivers true four-season warmth.
Draft Protection & Heat Retention
Every opening in a sleeping bag represents a potential heat leak, which is why we engineer multiple draft barriers into the Polar Ranger. The insulated draft collar sits around your shoulders and cinches down with a single-pull cord, creating a seal that traps warm air inside the bag. The hood features a two-cord adjustment system—one tightens the face opening, the other shapes the hood around your head—letting you dial in the perfect seal without feeling constricted.
The full-length zipper includes an insulated draft tube that runs the entire length of the closure, preventing the cold metal teeth from creating a thermal bridge. We use a YKK zipper with anti-snag sliders that glide smoothly even when you’re wearing gloves, and the zipper garage at the top prevents the slider from catching your chin or catching fabric when you’re sealing the bag from inside.
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Common Questions About the Polar Ranger Sleeping Bag
The Polar Ranger carries a comfort rating of -20°F (-29°C) and a lower limit rating of -34°F (-37°C) using EN testing standards. The comfort rating represents the temperature at which a cold sleeper will stay warm through the night, while the lower limit indicates the temperature at which a warm sleeper can still sleep without shivering. We recommend using the comfort rating as your guide when selecting a bag for your planned conditions.
The Polar Ranger uses Nikwax Hydrophobic Down synthetic insulation that resists moisture absorption significantly better than untreated down. When exposed to condensation, light precipitation, or humid conditions, the treated synthetic fibers maintain their loft and continue insulating even when damp. Traditional down bags lose 50-70% of their warmth when wet, while the Polar Ranger retains most of its thermal efficiency. This makes it ideal for coastal mountains, spring expeditions, and any environment where you'll encounter moisture.
Yes, the Polar Ranger features SynergyLink Connectors that snap directly to compatible Therm-a-Rest sleeping pads including the NeoAir XTherm, MondoKing 3D, and ProLite series. The connectors attach to loops on the underside of the bag and corresponding points on your pad, creating an integrated sleep system. This prevents you from rolling off your pad during the night and eliminates the gap between bag and pad where cold air can infiltrate.
The regular Polar Ranger measures 6 feet in length with a shoulder girth of 62 inches and accommodates users up to about 6 feet tall. The long version extends to 6 feet 6 inches with slightly wider dimensions throughout, designed for users between 6 feet and 6 feet 6 inches tall. The long size adds approximately 6 ounces to the total weight. Choose your size based on your height plus room for layered clothing and the ability to tuck extra insulation at your feet.
Wash the Polar Ranger in a front-loading machine on gentle cycle using technical down wash or synthetic insulation cleaner. Rinse twice to remove all soap residue, which can degrade the hydrophobic treatment. Tumble dry on low heat with clean tennis balls or dryer balls to break up clumps and restore loft—this takes 2-3 hours. Never dry clean the bag. For storage, use the large storage sack we include and hang the bag in a closet or lay it flat in a dry location. Never store the bag compressed in its stuff sack, as this breaks down insulation over time.
The Polar Ranger is optimized for winter conditions below 20°F, and most users will find it too warm for spring and fall camping when temperatures stay above freezing. The two-way zipper provides some ventilation flexibility, but if you're planning trips where overnight lows range from 20°F to 40°F, consider a bag rated to 0°F or 10°F instead. We design the Polar Ranger specifically for expeditions, winter mountaineering, and cold-weather camping where serious insulation is required.
For true winter camping at the Polar Ranger's rated temperatures, pair it with a sleeping pad rated R-value 5.0 or higher. The NeoAir XTherm at R-value 7.3 is our top recommendation for extreme cold, while the MondoKing 3D at R-value 7.0 offers more cushioning for car camping. Your sleeping pad provides the insulation between you and the frozen ground—a warm bag over a low R-value pad will still leave you cold from below. We consider the pad-and-bag combination as a single sleep system when engineering for specific temperature ranges.