So, when it's summer in the northern hemisphere, it's winter in the southern hemisphere. When the North Pole of the Earth is tilted toward the Sun, we receive more sunlight and the days are longer. This increases the amount of light that a given area on the Earth receives. More sunlight means more warmth, or summer. When the North Pole is tilted away from the Sun, the days are shorter and the Sun does not rise as high in the sky.
Less sunlight means less warmth, or winter.
Even though there is more sunlight in the summer, it takes time to warm up the Earth and the atmosphere. So the heating and cooling effects from greater and lesser sunlight have a delay of almost two months. Many people think so, but this is not the main reason. At noon tomorrow, measure the same shadow again. Be sure to make your measurements carefully at the same time each day.