I use this in my greenhouse to turn on an exhaust fan at about 85f. It works extremely well. (back order now, but there may be other sources on line).
http://www.charleysgreenhouse.com/i...=3136&s=thermostat&cid1=-99&cid2=-99&cid3=-99
http://www.charleysgreenhouse.com/i...=3136&s=thermostat&cid1=-99&cid2=-99&cid3=-99