This bag is a gloriously cozy cocoon to nestle within and, with a comfort limit of -15°C (5°F), it is wonderfully toasty in all but the most Baltic conditions. However, it's limited to sub-zero use, as its elasticated expander panel allows the user to open things up, thus regulating the temperature inside. Even if it’s cold and rainy outside, that doesn’t mean you can’t enjoy your outdoor activities! With the best 4 season sleeping bag, you can experience optimal warmth and insulation in the outdoors.

A zip baffle is a flap of cloth placed behind the zipper to keep heat from leaving the sleeping bag’s inside. On the other hand, a zippered cover conceals the zipper mechanism. This design provides a secure functionality that prevents the sipper from being undone. The zip cover also serves as an additional layer of insulation.Four-season sleeping bags are available in a choice of synthetic or down fillings. Synthetic sleeping bags are filled with artificial polyester fibres that are less expensive and more durable. In addition, when wet, they retain their functionality compared to down. They don’t, however, provide the best warmth-to-weight ratio. Snugpak’s polyester Softie insulation has been a mainstay in the British brand’s products for over thirty years. It utilizes superfine yarns bound together with special resins to mimic the properties of natural insulation such as down. The result is a really plush feeling bag that is easily warm enough for winter camping trips. Made for adventurers who won’t likely camp when it’s much below freezing, REI’s Down Time 25 has the bells and whistles to make sleeping out great, as well as a robust and verified eco story. The Exped Waterbloc Pro sleeping bag is a 4-season sleeping bag designed with bivying in mind. It has 800 fill down, making it very soft and warm, with a Pertex outer shell that repels the weather.

Mummy sleeping bags are also more lightweight. Additionally, you can also find double sleeping bags in various shapes to accommodate more than one sleeper. Made from extremely light and compressible Responsible Down Standard-certified insulation that’s been treated to repel water, this bag has several distinguishing features.The person inside the sleeping bag will not feel cold or uncomfortable at this temperature. The limit rating is similar to the comfort rating, except it applies to an adult man rather than a female. The upper limit is the maximum temperature at which an adult may sleep without sweating or experiencing discomfort.

On the other hand, a two-season sleeping bag is perfect for the late spring to early fall months, providing warmth up to 5 degrees Celsius. During the late fall or mild winter evenings, the three-season sleeping bag can withstand temperatures as low as 0 degrees Celsius. Finally, the four-season sleeping bag provides protection in temperatures as low as -5 degrees Celsius on chilly winter evenings. There are four different zipper systems available for sleeping bags. These include full-zip, three-quarter zip, half zip, and double zip. A double zip is an excellent choice since it allows for optimum ventilation and temperature control. Ideally, opt for a zipper system equipped with a zip baffle. As zips can allow for heat to escape, a good winter bag will also come with baffles along the length of the zip that seal everything in once it’s closed. A baffle will often be present around the shoulders to cinch down and tighten everything up, thereby preventing any heat from escaping through the night. Combine with a good sleep systemFour-season sleeping bags come in a variety of types. When unzipped, standard sleeping bags are usually rectangular, allowing you more room to walk around. You may also use regular sleeping bags as a blanket. During warmer weather, a 4 season sleeping bag can still be used, especially the more expensive options on the market which typically offer superior breathability, making your nights more comfortable and enjoyable. Moreover, you get to enjoy optimal airflow, which can help combat the heat via ventilation to keep you cool if you’re burning up.

The Kelty Cosmic Down 20’s is unusual in that it uses trapezoid-shaped baffles to provide insulation. The dog approves (Image credit: Kelty) InsulationThe OEX Leviathan EV 900 has an impressive comfort rating but we wouldn’t recommend bivying in it (Image credit: Craig Taylor)