What temperature rating do I need for summer camping?

For most U.S. summer conditions at low to moderate elevation, a 40°F to 50°F comfort rating is plenty. If you're camping in deserts or above 7,000 feet where nights drop into the 30s, look at a 30°F bag or pair a 40°F quilt with a base layer. Treat manufacturer ratings as optimistic unless the bag carries an EN/ISO rating, which specialist subreddits repeatedly emphasize.