It decreases. Because the time the sun is above the equator is maximum at the equator and the time to cool off is minimum. Consider an extreme. At the extreme north/south travel of the sun, it only touches near each pole once per year. Then there is a whole year to cool off as the sun goes to the opposite extreme and back again. If you go a little south of the northern extremity of travel or a little north of the southern extremity, it is a little warmer because the exposure to the sun is not at the extreme minimum. At the exact center of travel, the equator, the maximum time away from that point is the minimum for any location on earth.