Get a blanket with a reflective underside.

A silver-coated reflective layer (like those “space blanket” style beach blankets) does the best job of staying cool. Light-colored cotton or a tightly woven polyester works okay in a pinch, but the reflective ones actually bounce the sun’s heat away rather than absorbing it.

The problem with most blankets is they soak up solar energy like a black car on asphalt. Fleece, dark colors, thick cotton – all bad ideas. Reflective blankets are thin, fold up tiny, and keep the ground temperature surprisingly reasonable. You can find them online for $15-20.

Your back will thank you.