Note #1 Absolute pressure v. Gauge pressure - What on earth is NDT talking about? The effect on the pressure in a football due to a change in temperature is one of the easiest physics problems there is. The formula is PV = nrT. Solve for the change in P by dividing by V. Everything but T is constant so the change in pressure is the ratio of the new temp. to the old temp. If you fill the ball in a 90 degree room and take it to a 20 degree environment the pressure will be 22% lower in the ball. If you start with 13#'s in the ball you would end with about 10#'s in the ball.