Through the year, the path of the sun across our sky changes. In the summer the sun comes closer to being directly overhead than it does in the winter. That means the sun's light is more direct, and it's easier to be burned. When the sun is lower in the sky in the winter, its energy is spread out over a larger area. The difference between the sunlight in summer and in winter is much larger than the difference between solar maximum and solar minimum.
Clouds are important, too.
A thick layer of clouds absorbs even more of the sun's ultraviolet light. So on a cloudy day we have a little more protection than on a clear, sunny day. There's no reason to worry about changes in the sun during its natural cycle. We are safe on the ground, protected by the earth's atmosphere. But we should still be careful to protect our skin from too much sun.