Is summer hotter because earth is closest to the sun during this time?

No. In fact Earth is at its farthest point from the sun in early July and at its closest point in January. Earth's axis of rotation is tilted so relative to its orbit, so each hemisphere is alternately tilted toward and away from the sun. When the northern hemisphere is tilted toward the sun it experiences summer while the Southern Hemisphere, which is tilted away, experiences winter. When a hemisphere is tilted toward the sun, sunlight strikes the surface there at a steeper angle, so the sunlight is less spread out than it would be hitting at a shallow angle. The more concentrated sunlight results in greater heating.