What conditions are important in determining if it will rain or snow?

For snow to fall to the ground, the temperature must be cold both up in the clouds where snowflakes form, and down at ground level. If the air near ground level is too warm, the snow will melt on its way down, changing to rain or freezing rain. Moisture is needed to form clouds and precipitation.

Well for snow to fall to the ground, the temperature has to be 32 degrees. And it has to be cold in the clouds where snowflakes form and fall. If the air at ground level is warm or above 32 degrees, the snow will melt half way down to the ground and the snow will just change to rain.