Are sheepskin seat covers hot to sit on in summer?

No, it is exactly the opposite . Wool keeps you cool in summer and warm in winter. Wool is a great insulator but when we think of wool warm comes to mind and vice versa an Esky which is also an insulator keeps our drinks cold. Both an esky and wool can keep you warm or cool. We make twice as many seatcovers here in Queensland in Summer against our winter, because leather can get so hot in the sun.