Portable cloud

Every years some stretch of blazingly hot cloudless days will come by and cook a few cities, causing dozens to die from heatstroke. Since nature did not see it fit to provide any shade from coulds that might provide relief, it's up to us to provide a half-baked solution!

The Portable Could would consist of thin reflective plastic tubes filled with helium, which support a thing mylar shield. The Portable Cloud can be pumped up and secured by ropes over a city to provide shade like a giant parasol, and the cost defrayed by advertisements along the underside. Most airports tend to be at the perimeter of a city, so it shouldn't be that much of a problem.

Alternatively, if the use of helium is too expensive, a plastic duct carrying hot air from the city's incinerator, power plant, or center of government can provide the necessary lifting power to the balloon tubes.