Final answer:
The density of newly-fallen snow is primarily affected by temperature and humidity because these factors influence moisture content and the type of snowfall.
Step-by-step explanation:
The two PRIMARY factors affecting the density of newly-fallen snow are temperature and humidity. These factors are crucial because the temperature influences the amount of moisture air can hold; warmer air can retain more moisture, leading to different types of snowfall. Humidity impacts the moisture content of the snow itself. Areas that are colder will typically have lighter, less dense snow because cold air can hold less moisture. Conversely, warmer air that can hold more moisture will result in a wetter, denser snowfall. Wind speed, altitude, cloud cover, sunlight, and atmospheric pressure can also affect snowfall, but they are not as primary as temperature and humidity.