All of the thermostatically controlled fan clutches (the ones with the spring on the front side) I have gotten in the last several years have been factory set to lock up at 210 degrees. So basically on hot days out here that’s where my cars run (but I’ve never had one go over that as long as the clutch was good).

On a side note, if the spring on the front of the clutch is tightened (usually ½ a turn at a time), it will lower the temperature the clutch locks up).