Today, the sun seems extremely bright; more dazzling than usual, and even the roads seem to be brighter so it's not just when you look up in the sky. Is more light actually getting through (perhaps there is less moisture in the air than usual to refract the sun's light?) or is it just because, being winter, the sun is lower in the sky and I notice it more? But then, why wouldn't I notice it the same every day in winter?
The cooler winter atmosphere contains less water vapor, which results in less attenuation of incoming solar energy. Therefore, it would seem brighter. Note however, that winter lower altitudes of the Sun mean that we view it through more atmosphere, which reduces its apparent luminosity.