Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.
It really doesn't matter which way the electrons flow, other than the sparkplug polarity issue mentioned in the other thread. "Conventional" current flow (positive to negative) can be thought of as the movement of vacant electron sites ("holes") as the electrons move the other way...