The Thermal Chimney

Open the lowest windows on the coolest exterior wall of the house. Then open the highest windows in the house. Hot air goes out the top windows, creating a vacuum that pulls cool air in through the downstairs windows. That cooler air absorbs warmth, rises, and continues the cycle. This can also cool an attic. Install soffit vents for intake, and exhaust vents at the high point of the roof. A vented attic is generally about 20°C cooler than an unvented attic, and losing that hot air will help cool the upper floors.