If you are out in sunlight in the summer, there's not much doubt that the direct sunlight from the Sun feels warmer than it did in winter. The Sun itself hasn't changed so why is this?
This effect is caused by the Earth's atmosphere. When the Sun is lower in the sky, the sunlight has to travel through a thicker layer of the Earth's atmosphere than when it is higher in the sky. This extra thickness of atmosphere absorbs some of the radiation from the Sun and makes it feel less strong. This effect is especially important for ultraviolet light, which is why it is safer to be out in the Sun in the early morning and late afternoon rather than around midday