Most probably clouds, because, they hold rain, snow, hail, and when there are no clouds, the weather is beautiful, sunny and warm.
There are obviously more important factors which have an impact, like wind and the Sun, but the paramount impact caused would be by clouds.
weather
Sea, weather and visibility conditions.
Sea, weather and visibility conditions.
Oxygen is the most important factor for living things.
The most important factor in interviewing well is preparing for the interview.
The most important factor is the stars mass.
The most important factor is light.
weather maps
Relative salinity is the most important factor in seawater density.
What weather factors are most important to know in wild land firefighting?
Barometric pressure
The most important factor in an excellent golf swing is set up.