You are really asking about relative humidity. Air at different temperatures becomes saturated with moisture at different rates. So, warm air is able to be saturated with more mosture before it condenses into clouds/rain.... Cold air cannot retain as much moisture, therefore, you will normally see dew (which turns to frost) or clouds/sleet/snow. In other words... at 19 degrees, the air is saturated with moisture to 87% of its capacity. That is not the same amount of moisture as 70 degrees with 87%humidity.
When the air becomes saturated, you get dew... When air holding as much moisture that is can cools, then that extra moisture has to go somewhere (condensate on the dust in the sky- clouds- gets too much moisture- precipitation)
