Well, I think youre missing the point. Sleeping bags are supposed to be warm! Ha, ha, ha!
You dont specify a desired temperature range, but given your California location, Ill assume youre looking at nighttime lows in the 40s or even 50s. REIs Travel Sack +55 ($59; rei.com) is a warm-weather bag thats really not much more than a light blanket. It zips up, but also fully unzips and lies flat. For a slightly warmer bag, the Big Agnes Nugget 45 ($189; bigagnes.com) uses excellent Primaloft insulation. It has no insulation on the bottom, based on the assumption that youll be on a pad. So it doesnt unzip into a comforter.
Speaking of comforters, why not just get a Primaloft comforter? You can find them in Full or Queen size on the Web for around $100. I like Primaloft for this application because it resists water so well, just in case it somehow gets wet.
The third option is to buy a sleeping bag liner and use that as a super-light bag. Marmots Trails Bag ($79; marmot.com) consists of a breathable nylon shell with a light lining of brushed Micro DriClime, a fuzzy, wicking material that feels soft and keeps your skin dry. If it had a temp rating it likely would be around 60 degrees. Cocoon (available at rei.com) also makes bag liners that are designed to add warmth to regular bags, and help keep them clean, but that also work well as standalone sleepy things in warm climates. Theyre available in silk ($50), flannel ($30) and cotton ($20).
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