Weather conditions have a big impact on the quality of natural light. On an overcast day, clouds will diffuse the sunlight and shadows will become less severe. Similarly, mist and rain can further soften and cool the light.
The time of year also plays a part. It depends on where you are in the world, but generally in winter, the tilt of the earth means the sun is farther away, making the angle of light more acute. So even though the days are shorter, we effectively have more directional light to work with. On the other hand, during the summer, the sun reaches a higher apogee in the sky, so it's more top-down and less photo-friendly during the hours around noon.
"Your choice of settings can be more complicated to manage in winter, when shooting snow or cloudy skies," explains Canon Ambassador Sebastien Devaud. "It's better to increase your exposure a little, compared to the auto exposure setting, so the snow or the sky appear more white than grey. Shooting in black and white is a good way to enhance the dramatic side of this season, while fog, mist, low cloud or water can also add a particular mood to winter shots."