To prepare for extreme heat, you should:

Install window air conditioners snugly; insulate if necessary.
 

Check air-conditioning ducts for proper insulation.

Install temporary window reflectors (for use between windows and drapes), such as aluminum foil-covered cardboard, to reflect heat back outside.

Weather-strip doors and sills to keep cool air in.

Cover windows that receive morning or afternoon sun with drapes, shades, awnings, or louvers.
(Outdoor awnings or louvers can reduce the heat that enters a home by up to 80 percent.)

Keep storm windows up all year.