How many gal .of water does it take to fill a cubic foot?

It takes 7.48052 gallons of water to fill a cubic foot.

From wikipedia:

The U.S. liquid gallon is legally defined as 231 cubic inches,[2] and is equal to exactly 3.785 411 784 litres (1 L = 10−3 m3) or 0.133 680 555… cubic feet. This is the most common definition of a gallon in the United States. The U.S. fluid ounce is defined as 1/128 of a U.S. gallon.

One cubic foot is equal to 12 inches x 12 inches x 12 inches, which is 1728 cubic inches.

Therefore,

(1728 cubic inches / cubic foot) * (1 cubic foot / 231 cubic inches) = 7.48052 gallons

In this case, the temperature of the water does not matter, because a liquid gallon is defined as a measurement of volume, not of weight.