On November 12, 19985, U.S. Patent No. 4,551,857 issued to Aaron A Galvin on a Hot Weather Hat:

Providing cooling in a hat has been a hot topic for inventors.

On November 21, 1967, U.S. Patent No. 3,353,191 issued on a Cooling Unit for a Hat:

On December 22, 1970, U.S. Patent No. 3,543,415 issued on an Air Conditioned Helmet:

On November 20, 1984, U.S. Patent No. 4,483,021 on a Thermo-Electric Cooled Head Gear: