Well, I think you聮re missing the point. Sleeping bags are supposed to be warm! Ha, ha, ha!
Marmot Trails Sleeping Bag/Liner
Trails Sleeping Bag/LinerYou don聮t specify a desired temperature range, but given your California location, I聮ll assume you聮re looking at nighttime lows in the 40s or even 50s. REI聮s Travel Sack +55 ($59; rei.com) is a warm-weather bag that聮s 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 you聮ll be on a pad. So it doesn聮t 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. Marmot聮s 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. They聮re available in silk ($50), flannel ($30) and cotton ($20).
Get a sneak peak of 国产吃瓜黑料聮s picks for . The complete 2007 Buyer聮s Guide, featuring 400-plus gear reviews of this summer聮s must haves, is coming soon to 国产吃瓜黑料Online.