since polyester does not 'breath' it tends to be a warmer batting. cotton breaths- so is great for warm weather quilts- wool is another good choice- the quilt we have on our bed in the summer has a wool batting-may seem strange but it is wonderfully lightweight, lofty, breaths - is warm in the winter & cool in the summer. when someone complains they do not like quilts because they are not warm- I make them one that is warm...I use warm fabrics (like flannels, wools, corduroy's, denim and I use either a wool or a polyester batt...I also remind people that back in the days when women were making quilts to keep their families warm they layered bed linens...a wool or cotton blanket {or what ever they had) and a quilt or 2- their quilts were made with homespuns, cottons, wools, again- what ever they had ...